Go++

Go playing program. Winner of numerous international computer Go tournaments. The result of twenty years research and development.

GNU Go

A free cross-platform computer go opponent.

Sensei's Library

A collaborative web site about and around the game of Go, where anyone can freely contribute information and participate in discussions.

Go4Go Database

A portal containing game records, news, and a discussion forum.

GoDiscussions.com

Forum with instructions and commentary for beginners to professionals. Also includes a game analysis and study section.

GoBase.org

An encyclopedia of go topics, including rules, stories, tournaments, computers, and resources for the study and enjoyment of the game.