GoBase.org:An encyclopedia of go topics, including rules, stories, tournaments, computers, and resources for the study and enjoyment of the game.
Game of Go Webring: Contains sites with clubs, game information, and downloads.
GoDiscussions.com: Forum with instructions and commentary for beginners to professionals. Also includes a game analysis and study section.
Sensei's Library: A collaborative web site about and around the game of Go, where anyone can freely contribute information and participate in discussions.