an "official" website dedicated to the setting created and maintained by Peter Gifford. The site recently underwent an overhaul and is very attractive indeed, with sections devoted not just to the setting itself but also to gaming on Tékumel. There are forums and archives, too, the latter being especially interesting, since it includes a wide range of older resources.
It's an extremely good and useful website. If you have even a passing interest in one of the great settings of our hobby, you owe it to yourself to visit Tekumel.com.