The most densely populated area of Africa, it is many ways both the continent's most difficult place for travel and potentially its most rewarding.
The African highways connect many cities in West Africa with Nigeria being the main hub.
Flying from other African cities can be dangerous as many airlines have a very poor safety record. Check this first before choosing to fly with an airline.
In order of size here are the main airline hubs.
Generally it takes time - and a whole lot of patience - to move around in West Africa. The roads are not all in great conditions and many roads aren't paved. Always be sure to have an extra day or two in the end if you are going somewhere since planning is very hard when the transport is unreliable.
Well, there actually isn't too much to see here! Visitors who focus on sightseeing will find themselves experiencing a lot of hardship with pretty small payoffs. A common traveler complaint is of spending the whole trip in miserable bush taxis! The big game animals of the rest of Sub-Saharan Africa are absent; the majestic ruins of North and East Africa likewise are nowhere to be found. Many would argue that time spent searching for "attractions" would be better spent getting to know the people you are visiting, engaging in a real and meaningful cultural exchange: starting to understand their history, religious practice, and way of seeing the world, and sharing a bit of your own.
That said, though, we're all travelers here, it's hard to stay in one place, and chasing down sights is a good way to slake wanderlust.
Historical monuments dating back past the arrival of Europeans in the region are few and far between. Tropical weather took its toll upon the larger structures built by old kingdoms and empires, and those that survived the weather often were destroyed with some incredible violence by European invaders (the destruction of Benin City in Nigeria being a prominent example). The most notable structures of African past would likely be the enormous collection of ramparts, walls, and ditches at the ancient fortress of Sungbo's Eredo, less than 20 miles from Lagos (and the largest pre-colonial monument in the whole of the continent), and the palaces of the Dahomey Empire in Abomey, Benin. Also in Nigeria, Kano holds much interest (and is generally one of the most pleasant places for a tourist to visit in the country) as the seat of the historical Empire of Kano, with the Emir's palace (in addition to other sixteenth century sites around the city) being fully intact, albeit much renovated throughout the centuries.
Many of the sites of significant historical interest in West Africa are European-built. The terrifying slave castles of the Ghanaian coast (most famously at Elmina and Cape Coast) are imposing on their own for their massive size and seaside locations, but their importance to the history of the modern world cannot be overstated, and are a must-see for anyone in the region. Sites of importance to the slave trade are hardly limited to the charismatic forts of Ghana, though, with prominent sites near Dakar, Conakry, Ouidah, aforementioned Abomey, Porto Novo, and Freetown (with sites especially important to the slave trade to the United States in Freetown).
Modern Africa has in recent years ramped up its production of monument building, epitomized by the colossal African Renaissance Monument outside Dakar, intended to challenge perceived foreign perceptions of African as an inferior backwater. Other monuments, such as the Arch 22 in Gambia, the Nkrumah Mausoleum and Independence Square in Accra, and others throughout the region's national capitals are more concerned with less lofty ideals of good old fashioned national greatness and deification of postcolonial leaders.
The culture's of West Africa are deeply religious, and much of the cultural life and monuments revolve around spirituality. Of muslim architecture, most travelers find the mud-built Sudano-Sahelian mosques to be of the most interest. The region's most famous, both of the Volta basin style, include Larabanga Mosque just outside Mole National Park in Ghana and the Grand Mosque of Bobo-Dialassou. A bit less unique, but still impressive, are the capital-type, modern grand mosques in Abuja, Lagos, Ouagadougou, and other major cities in the region.
For Christian architecture, the most obvious place to visit is the Basilica of Our Lady of Peace in Yamoussoukro. The basilica is in fact the largest church in the world, ahead of St. Peter's Cathedral in the Vatican, from which its more modern design draws inspiration. Other interesting Christian buildings include the curiously mosque-like Dakar Cathedral and the strikingly modern St Paul's Cathedral in Abidjan.
But lets be serious, you can go anywhere in the world to see great works of Christian and Muslim architecture—lets get to the Voodoo! Benin is the spiritual homeland of voodoo (which shares much in common with traditional religious beliefs throughout West Africa) and neighboring Togo is another center of widespread Vodun practice. Cotonou's Grande Marche du Dantopka is the world's epicenter for purchasing voodoo fetishes, full of monkey skulls, lion paws, and all sorts of other less offensive charms. Lomé's Marche de Feticheurs is likely the second biggest fetish market in Africa, albeit a bit more touristy—they charge for admission! Voodoo is a bit more occulted in Ghana and Nigeria, but still very much present (try searching Jamestown in Accra for the "timber market"). Shrine-like voodoo fetishes are scattered throughout Togo and Benin, with the largest being Dankoli fetish near Savalou. Togoville is the center of voodoo practice in Togo, and its fetishes and shrines are unusually juxtaposed against its large cathedral, which saw a papal visit in 1986!
Ghana is also a rewarding destination for those interested in local religious and cultural beliefs. The Ashanti region around Kumasi is dotted with shrines...
Despite a large number of national parks, tourism in the wild is elusive in Africa's most crowded region. Moreover, a large number of West Africa's protected areas are in dire straights, undermined by political conflict and lawlessness, either current or historical. The most visited parks are those that are easiest to reach, in countries with decent transportation infrastructure. Ghana's Kakum National Park is in all honesty not that impressive, but is just off the main coastal road, and is extremely popular. Ghana's northern Mole National Park, on the other hand, is harder to get to, but still popular for its superior wildlife viewing opportunities. Nigeria's Yankari National Park similarly has good tourist infrastructure, and has actually become one of the top tourist destinations in the country. While none of Gambia's national parks has taken off as a standout tourist destination, the ease and popularity of visiting has made trips on the Gambia river a prime eco-tourism and birding activity.
Further afield, Taï National Park in Côte d'Ivoire is an incredible refuge of West Africa's once great biodiverse tropical rainforest. While the country's instability has made it more difficult to visit, it remains the country's most accessible. The trans-border W National Park is the region's highlight, but it is far enough off the main transportation grid to keep it quietly off the beaten path. Niokolo-Koba National Park is a great place for wildlife spotting in Senegal, but its remote southeastern location keeps the tourists away.
If you really want to get off-the-beaten-path, prepare for some serious adventuring. Tiwai Island, a refuge teeming with numerous rare monkey species, as well as the occasional pygmy hippopotamus, is theoretically not so hard to hard to reach, but Sierra Leone is hard enough to get to, and you will need some serious time to get there and do it justice. The biosphere reserve of the Bijagos Islands is similarly well set up for a visit, but it's just hard to get there, in rarely visited Guinea-Bissau. For the truly adventurous (or simply insane), Sapo National Park is in a terribly dangerous section of Liberia, requires a permit to visit (and is visited almost only by poachers), has no paths or roads, and no accommodations in or near the park. But it is a great refuge of West Africa's remaining tropical rainforest and its most rare species: forest elephants, pygmy hippopotami, monkeys, chimpanzees, et al.
West Africa is home to some incredible, mind-blowingly beautiful beaches, and they are not always where you would expect. Gambia, Cape Verde, and to a somewhat lesser extent Senegal are well known and well developed tropical beach destinations. But the most beautiful beaches (OK, don't tell Cape Verdeans this) are at Africa's westernmost point: Liberia and above all Sierra Leone, home to what are possibly the most beautiful beaches in the world. And, of course, Sierra Leonean and Liberian beaches are emphatically not overdeveloped—you will often have them to yourself, or share them with a few busy fishermen!
Beach duds, unfortunately, crop up in the Gulf of Guinea, where locals do not respect the their coast's great natural beauty. (Granted, eking out a decent existence in these poor countries often seems a greater priority.) The beaches anywhere near towns and cities are heavily littered, and are used as a toilet, filling the water with squishy feces. The beaches are also very dangerous in this region, both for being the home of the respective countries' highest rates of violent crime, and very strong currents. Of course, there are notable exceptions, particularly in the sparsely populated regions of western Ghana.
West African food doesn't seem to be for everyone, but those who like it love it. The staple dishes are starch plus some version of soup. Rice is the most popular starch, but fufu—a thick paste, with the rough consistency of soft play-dough, usually made by boiling starchy root vegetables in water and pounding with a mortar and pestle—and other similar pastes are a more interesting alternative. Fufu and its cousins should be eaten with the right hand, and usually dipped in the sauce, stew, or soup provided. Simple "chop bars" (there are plenty of different names for this common phenomenon) nearly always provide this recipe, plus some chicken or fish.
Street food is delicious, multifarious, and dirt cheap. Unfortunately, problems with sanitation make this food a bit more dangerous than those found in chop bar-style spots and restaurants, for the straightforward reason that you aren't sure when it was cooked! Items that you see cooked, items that require peeling (e.g., eggs, coconuts, bananas, etc.), or items wrapped immediately after cooking (like bread) are safe.
Restaurants in cities are very skewed towards European dishes, and tend to treat African food like a poor man's diet. The Francophone countries often have a few excellent French restaurants hidden in the larger cities. What constitutes a "restaurant," though, is malleable. The restaurant could potentially be just a log for sitting, and be defined a "restaurant" simply by dint of having more than three dishes available.
Make sure your water bottles are sealed and not just refilled with tap water. It can be hard to see until you actually test the top, but people are generally honest about this sort of thing. Many travelers try to go for the locally produced mineral water, rather than those produced by foreign corporations, since local economies need all the help they can get.
"Pure water" is also widely available in guaranteed-sanitary sachets sold on the street, usually for less than 5¢, and is a great way to make sure you stay hydrated in the hot climate. Coconuts in most of these countries are also omnipresent, and street vendors will take off the top with a machete for a tasty drink.
Lagers, non-alcoholic malts, and some weird beverage masquerading as "Guiness" are among the more popular beverages you will run across. Voodoo priests and chiefs seem to prefer Schnaps. For harder stuff, look around for palm wine and gin sachets (which mix well with sprite, or more foolishly, palm wine).
As far as disease goes, West Africa is the most dangerous place on the planet. It is probably the one place on earth where you should go to extremes to protect yourself from mosquitoes. Do not sleep without a net and do not go without malaria medicine. If you develop symptoms, go to a clinic immediately to make sure of whether you need treatment. Malaria is about as common here as a runny nose, and the worst strain (which is by no means uncommon) can kill you in 24 hours. The parasite will likely live with you for the rest of your days as well, with high risk of recurrence. There is no vaccine.
There are plenty of other scary tropical diseases to protect yourself from in this region. The other big dangers for which there is no vaccine available, include common Dengue Fever and Schistosomiasis, various other creepy parasites, Lassa Fever, River Blindness, and the more rare Ebola virus.
Many diseases, happily, can be prevented via vaccination. Visit a travel clinic before traveling to the region to find out exactly which immunizations you will need, preferably giving yourself ample time to get the shots taken care of! You need a yellow-fever vaccination to enter most (if not all) of these countries. Rabies vaccination is generally considered optional, but it is a terrible disease to get, with 100% mortality if untreated, and you're most likely to contract it far away from decent medical services.
Are the dangers posed by road travel really greater in West Africa than the rest of the developing world? Yes, probably. Travel by boat is notoriously unsafe throughout the region as well. Traffic accidents kill more travelers than disease in West Africa. There isn't a whole lot you can do about this, unfortunately. The most important step to take is to avoid overland travel after dark. Other steps available to those traveling more luxuriously would be to get a trusted driver with a larger 4WD vehicle, and to just generally avoid the rickety minivan bush taxis driven by fatalistic maniacs. Moto-taxis are quite unsafe as well (if often by far more convenient than any other form of transportation...).
West Africa gets a worse rap than it deserves for crime. Actually, it's possible this bad reputation is just Nigeria's fault. Outside that one crime-legend, West Africa just doesn't have the sort of problems with street crime that you'll find in East African capitals, in South Africa, or for that matter the United States! Countries such as Ghana, Sierra Leone, Senegal, Burkina Faso, Cape Verde, and most of Togo and Benin are so refreshingly free of violent crime.
Traditionally a volatile region, and, alas, currently a volatile region. The culprits are easily identifiable and avoidable, fortunately: Guinea, Liberia, Côte d'Ivoire, Guinea-Bissau, and to an extent Nigeria.