The Kara Tur boxed set in 2e had a lot of information, and the Kara Tur Trail Maps were the big printed maps on the subject.
The old 1e Oriental Adventures hardback had a small but very information intense writeup of Kara Tur in the back. You can get OA for 5 or 10 bucks on eBay.
In terms of 3e material, it's very sparse.
Crunchwise, there is the "Shou Disciple" PrC in Unapproachable East for fighters taught in Shou combat styles (essentially a fighter PrC that gets some monkish abilities), and a "Shou Expatriate" region for regional feats/benefits of a Kara Tur native living in Faerun. Dragon #315 had more elaborate rules for Regional feats/benefits for Kara Tur characters.
The continent of Kara Tur has several major empires, generally based strongly on historic asian nations:
Shou Lung - China at a peak of imperial might, development, bureaucracy, and civil service. The "main" empire of the continent.
T'u Lung - China at an era of increased era of corruption, nobles have much power of a figurehead emperor and nepotism and graft are widespread. Broke away from Shou Lung several centuries ago over a dispute on succession to the throne.
Malatra - Based on Southeast Asia and India. Lots of wild jungles, reminsicent of Malasia, India, Thailand, Vietnam ect.
Koryo - D&D version of Korea
Kozukura -Sengoku-era Japan (warring states, daimyo strugging for dominance)
Wa - Kamakura-era Japan (powerful central Shogunate)
Edit: Upon checking, Wizards.com has some of the original OA modules set in Kara Tur up for free download (
http://www.wizards.com/default.asp?x=dnd/dnd/downloads), in their "Previous Edition Downloads" section, you might want to check those out too.