You need your passport to get onto the island of Zanzibar. Be aware that the "porters" in Dar will hassle you for money and expect tips for referring you to "the best boat." If you don't want their help, be forceful. The dock is a zoo -- a prime hangout for pickpockets.
There are many ferries and catamarans that can take you between Dar es Salaam and the Island. Azam Marine is among the nicest available. It runs several times each weekday and costs between $35 and $40. The trip is beautiful and lasts about an hour. You might be able to find a cheaper ride, but remember: you get what you pay for.
Although taxis are available, you will probably want to walk through Stone Town. After all, most of the alleys are barely wide enough for a bike to pass.
Journeying outside Stone Town will require a taxi or a private car.
Zanziabr Island, a.k.a., The Spice Island, was an important stop in the Spice Trade centuries ago. Today, it is one of the few places in the world where saffron is produced, and many other Middle Eastern/Asian spices (cardamon, ginger, cloves, nutmeg, etc.) are grown here. For about $10, you can go on a spice tour, which winds you around the island, showing you how anise (licorice) grows; letting you sample some of the exotic fruit grown on the island; and allowing you to tour the beautiful plantations.
Jozani Forest has excellent nature trails, featuring some very exotic (and large) trees. Even more interesting, though, are the Red Colobus Monkeys that live here. Native to the Island, these monkeys are now nearly extinct. They are very curious and playful and will likely pose for a picture.
There are a number of historically important (and frankly, just plain beautiful) buildings in Stone Town, like The House of Wonders and The Arab Fort. It is easy to arrange a simple walking tour with a local guide who can teach you some history.
The market in Stone Town is one of the largest, most vibrant open-air markets anywhere. Here, you can find several varieites of bananas; "elephant garlic" unique to the island; the largest avocados you'll probably ever see; and more. Prices are extrememly reasonable. Even if you have no intentions of purchasing food, the spectacle alone is worth a visit.
There are a lot of things to do on Zanzibar Island. It just depends on where your interests lie.
Stone Town, recently declared a UNESCO World Heritage Site, is one of the most unique cities in the world. Blending Moorish, Middle Eastern, Indian, and African traditions and architectures, it is possible to spend days winding through Stone Town's labyrinthine alleys; shopping; drinking tea; and visiting the city's historic sites.
Be certain to have dinner on the wharf near Blue's Restaurant in Stone Town. Every evening, for just a few dollars, you can sample local fish, food, drinks, and hear local music.
The East Beaches are popular among travelers. The sand is brilliant white, and the warm waters of the Indian Ocean are a deep teal. Here, you can:
find plenty of opportunities to scuba dive;
swim with the dolphins;
arrange for a ride on a local's dhow (a carved, wooden boat);
Sit and stare at the water for hours on end.
Stone Town is a one-stop-souvenir-shopping for the traveler. You can find beautiful textiles, handmade jewelry, intricate wood or stone carvings, spices, knick-knacks, and the list goes on and on . . .
Blue's Restaurant, on the water, is an upscale restaurant you might find on any boardwalk anywhere. It's for that reason, however, that a visitor might not want to stop in. However, the food is great, and the view is gorgeous.
Although it is primarily a Muslim community, small bars are everywhere.
Blue's Restaurant makes excellent frozen drinks; they really hit the spot after a day getting lost among the maze-like alleys..
There are an unbelievable number of hotels on the island. In Stone Town, you might like:
Bottoms Up!, an eclectic, unusual hostel in the heart of Stone Town.
On the East Beaches, you might like:
Zanzibar is largely a Muslim community. Although they are used to Western ways, you should try to be respectful. This means:
Women and men should make an effort to cover their legs and arms.
Be discrete when drinking alcohol.
During Ramadan -- the month of fasting -- travelers should avoid eating and drinking during the daytime.
Zanzibar Island - page devoted to the island by the Tanzanian Tourist Board