Jed's THPS Videos: Video clips [avi] of combos in THPS 1 and 2. Also includes message board.
OnlineSkaters.net: Community site for the Underground series. Forum, screen shots, tournaments, and downloads.
PlanetTonyHawk: Information, FAQ, level guides, move and transfer lists, codes, glitches, downloads, and forum.
The Skate Park Emporium: Downloads, fora, links, and ratings regarding skate parks.
Tony Hawk Forums: Discussions on multiple games in the series as well as related topics.