Kansai (関西) is the western region of the main Japanese island of Honshu, second only to Kanto region of Eastern Japan in population. The area is also known as Kinki (近畿) District, literally "near the capital" (referring to ancient capital Nara and Kyoto), and its three big cities — Osaka, Kyoto, and Kobe — as Keihanshin (京阪神).
Differences between Kansai and Kanto (the eastern region dominated by Tokyo) are slight but numerous. Kansai people speak a distinctive dialect of Japanese, use lighter-colored soy in their cooking, ride on the other side of escalators and are renowned for humor and their love of food.
The Kansai dialect (関西弁 Kansai-ben) is Japan's largest dialect group after Tokyo's dialect group collectively. There are many subdialects, ranging from the elegant and effete Kyo-kotoba (京言葉) of Kyoto's courtiers to the gruff but imaginative gangster slang of Osaka, much favored by Japanese comedians. Some notable features include the copula ya instead of da, the negative ending -hen instead of -nai and the use of akan instead of dame for "No way!".
That said, most Kansaites are perfectly conversant in standard Japanese, so knowledge of the local dialect is by no means necessary, but even a few words will be appreciated. The typical Osakan greeting is Mōkarimakka? ("Making money?"), to which the typical reply is Bochi-bochi denna ("Well, so-so"); trying this out on a friend or acquaintance is guaranteed to produce a surprised smile, and make you look like a kettai (strange), aho (idiot) and omoroi (funny) guy.
English is taught at all schools in Japan, and while it is less commnonly spoken than in Tokyo you will find that younger people will often know enough English to communicate, especially those residing in the cities. Still, learning even a few important phrases in Japanese will be appreciated and not as difficult as many Westerners think.
There are three major airports in the Kansai Metropolitan Area. International flights land at Kansai International Airport. The primary domestic airport is Osaka's Itami Airport (officially called Osaka International Airport even though there are no longer any international flights). A new regional airport opened in Kobe in 2006, right across the bay from Kansai International — in fact, Kansai was originally supposed to be built there!
The three major cities of Kansai - Kyoto, Osaka and Kobe - are connected by a myriad of train routes. When traveling between two of these cities, it helps to determine what method of transportation fits your travel needs, and fits your budget... unless you have a Japan Rail Pass, of course.
Besides the Shinkansen, Japan Railways operates the main trunk line - the Tokaido Line - between Kyoto, Osaka and Kobe. The Kyoto-Osaka segment is known as the JR Kyoto Line, while the segment from Osaka to Kobe is the JR Kobe Line. The Special Rapid, or Shin-Kaisoku (新快速), generally leaves every 15 minutes with very fast transit times. If you do not have a Japan Rail Pass, however, JR can be more expensive compared to private railways.
The JR Kyoto Line connects Kyoto Station in southern Kyoto with Osaka Station in northern Osaka, stopping at Shin-Osaka for the Tokaido and San'yo Shinkansen trains. 28 minutes between Kyoto and Osaka via Special Rapid, ¥540. Free with the Japan Rail Pass.
The Hankyū Line (阪急) runs from central Kyoto, starting at Shijo and Kawaramachi streets. Trains exit Kyoto to the west and run into the massive Hankyū Umeda Terminal, located to the north of JR Osaka station. Limited express trains depart every ten minutes during most of the day. 45 minutes between Kawaramachi and Umeda, ¥390. Not vaild with the Japan Rail Pass.
The Keihan Line (京阪) runs from eastern Kyoto, starting from Demachiyanagi or Sanjo Street and operating parallel to the Kamo River past Gion and Kiyomizu Temple. Trains exit Kyoto to the south and run into central Osaka. After stops at Kyobashi (along the JR Osaka Loop Line) and Tenmabashi, the line splits: the main line runs to Yodoyabashi, while the Nakanoshima Line runs to Nakanoshima island. The fastest trains depart every ten minutes during most of the day. 51 minutes between Sanjo and Yodoyabashi, ¥400. One hour between Sanjo and Nakanoshima, ¥460. Not valid with the Japan Rail Pass.
If you do travel via the Keihan, an interesting thing to listen out for are the departure melodies - songs that are played before the train departs a station. Composed by Casiopea keyboardist and railroad enthusiast Minoru Mukaiya (向谷 実), each departure melody is part of an entire song - you will hear all parts of the song if you travel along the full route.
Another private railway that runs into Kyoto and Osaka is the Kintetsu Line (近鉄). However, traveling via Kintetsu between the two cities is not recommended. Services run on separate lines requiring you to change trains, and the total travel time is not worth the cost. On the other hand, Kintetsu is a great way to travel between Kyoto and Nara.
To go from Kyoto to southern Osaka (where Kintetsu trains terminate), you would be better off taking one of the other routes listed above; when you reach Osaka, change to the southbound Midosuji subway line and get off at Nanba.
The JR Kobe Line connects Osaka station in northern Osaka with Sannomiya and Kobe stations in Kobe; Sannomiya station is more centrally-located. 20 minutes between Osaka and Sannomiya via Special Rapid, ¥390. Free with the Japan Rail Pass.
The Hankyū Line runs from Umeda to Sannomiya, running to the north of the JR Line. Limited Express trains leave every ten minutes during most of the day. 27 minutes from Umeda to Sannomiya; ¥310. Not valid with the Japan Rail Pass.
The Hanshin Line (阪神) runs from its own Umeda station, south of JR Osaka, to Sannomiya, with trains continuing on to Himeji. Limited Express trains leave every ten minutes during most of the day. 29 minutes from Umeda to Sannomiya, ¥310. Not valid with the Japan Rail Pass.
Hanshin trains also run from Namba station in southern Osaka. Most services are a one-seat ride, otherwise you will have to change trains at Amagasaki. 45 minutes via Rapid Express, ¥400. Not valid with the Japan Rail Pass.
The JR Kyoto and Kobe Lines connect Kyoto with Sannomiya and Kobe stations. 50 minutes from Kyoto to Sannomiya via Special Rapid, ¥1050. Free with the Japan Rail Pass.
The Hankyū Line connects central Kyoto with Sannomiya, with a change of trains at Juso (north of Umeda) necessary. About 70 minutes from Kawaramachi to Sannomiya via Limited Express, ¥600. Not valid with the Japan Rail Pass.
Kintetsu trains run from the historical city of Nara to Sannomiya station on the Hanshin line via Namba. Direct trains leave every 20 minutes, reaching Sannomiya in 75 minutes at a cost of ¥940. Not valid with the Japan Rail Pass.
Most of Kansai's regional transportation companies have tied up to offer the ICOCA tickets, which can be used on pretty much any train, subway, monorail, cable car or bus in the region. The Nankai and JR trains from Kansai Airport are also included, and you can buy your card or pass at the airport's train station.
The ICOCA card  is a contactless smart card that can be used on JR West, JR East (Tokyo) and most private rail and bus companies in Kansai and Chugoku (Okayama, Hiroshima). Cards are available at ticket vending machines in train stations for ¥2000, including a refundable ¥500 deposit. More money can be added at the same machines.
The Surutto Kansai magnetic card is similar to ICOCA, but it doesn't work on JR and is not rechargable, making it pretty much obsolete.
The Kansai Thru Pass can be purchased as a two-day (¥3800) or a three-day (¥5000) pass. It is valid for two/three separate days within the validity period which is printed on the back (usually a couple of months). It can be used on most non-JR trains and buses (and even some cable cars) in Kyoto, Osaka, Kobe and Nara with the notable exception of JR trains. The service area extends south to the Kansai International Airport and the city of Wakayama and southeast to Mount Koya (Check the Area Map on the webpage for details). In addition to free transport, these tickets offer a series of small discounts to temples, museums and other attractions in the region. Be aware that you'll have to travel quite a bit to make them pay off. (Note: You might be asked to show your passport when you purchase this card.)
JR-West also offers the Kansai Area Pass, which costs ¥2000/¥4000/¥5000/¥6000 for 1/2/3/4 days respectively and is valid for unlimited travel on JR standard and Haruka limited express trains (non-reserved seats only). The area covered is approximately the same as for the Kansai Thru Pass above. There is also a more complicated route-based JR 4-day pass for different routes in the Kansai area called the Kansai Passport.
With its political and geographical significance in the history of Japan, the region of Kansai possesses three quarters of Japan's "National Treasure" buildings, half of its "National Treasure" artworks, as well as five UNESCO World Heritage Sites, making it an unmatched destination for heritage tourists to Japan.
Kyoto and Nara are both ancient capitals of Japan chock-a-block with temples and historical sites.
Kansai cooking is subtly different from the Kanto style, although the average short-term visitor is unlikely to spot many differences. Perhaps the most visible differences are a tendency to use light-colored soy instead of dark, especially in soups, and a preference for thick white udon noodles over the thin buckwheat soba noodles of eastern Japan.
Some famous Kansai dishes include:
sabazushi (鯖寿司 mackerel sushi), Battera of Osaka, sabazushi in Kyoto, or kaki-no-ha zushi (柿の葉寿司) from Nara are local variants of this type
okonomiyaki (お好み焼き), variously described as Japanese pizza or pancakes. Although Hiroshima also makes a strong claim for this name, they are in fact reasonably different from each other. (Hiroshima style tends to come cooked on a pile of noodles.)
takoyaki (たこ焼き) is the common name for the fried balls of octopus and batter. Akashiyaki (明石焼き) from Akashi City area is recognized as the origin of the more famous Osaka-style takoyaki. As opposed to the Osaka-style being served with dark and thick sauce on it, Akashiyaki are eaten without sauce but dipped into clear soup. When visiting takoyaki bars, the various fillings mentioned are generally substituted for octopus, rather than being an addition.
beef (和牛), there are famous beef brands; Kobe beef (神戸牛), Matsusaka beef (松阪牛), Tajima beef (但馬牛) and Omi beef (近江牛).
udon (うどん) is the popular noodle in Osaka instead of soba in Tokyo. Another udon area, Sanuki in Shikoku, is famous for delicious noodles, while Osaka is famous for delicious soup.
Kansai is sake country, with Nada (in Kobe) and Fushimi (in Kyoto) alone accounting for 45% of the country's production. Kobe in particular is a good place to tour sake breweries, many of which are open to visitors.
This is a usable article. It gives a good overview of the region, its sights, and how to get in, as well as links to the main destinations, whose articles are similarly well developed. An adventurous person could use this article, but please plunge forward and help it grow!