Introductions to go aimed at beginners.
A Wiki about the game of go: everybody can add comments, and corrections, or even create new pages. Created in November 2000 by Arno Hollosi and Morten Pahle, it now (August 2006) contains close to 14,000 pages, and is steadily growing further.
Several excellent article series by Charles Matthews, covering the basics of go, but also very advanced material, like the 10 articles on ko.
A pdf with a Korean and English introduction to go
A nice, interactive introduction to the game of go.
Introduction to go on the 9x9 board (pdf).
A short introduction to go in German.
An introductory site in Dutch.