Sensei's Library is the definitive online Go resource. This wiki-based site contains thousands of articles, lessons, problems, discussions, and a whole lot more. Be careful, many have reported signs of SL Addiction.
Life in 19x19 is the largest English Go forum, with ongoing discussions of every Go-related topic imaginable.
Online Tutorials for Beginners
While much has been written on the subject, the Wikipedia entry offers a comprehensive overview of the game, history, philosophy, and rules.
The Interactive Way To Go - This excellent Java-based tutorial will have you understanding the rules and ready to play in no time.
GoGameGuru - Another good set of beginning tutorials; the main website also has a lot of great articles and resources.
KGS Tutorial - A tutorial offered from one of the premiere Go servers, KGS.
GoProblems.com - A collection of interactive problems at all skill levels, good for beginners and dan players alike.
The Online Go Server - OGS is a very user-friendly online Go server, with a streamlined interface and excellent game review tools. It is entirely browser-based, with no client download, and is accessible from almost all computers or from your mobile phone.
The KGS Go Server - KGS is one of the more approachable online Go servers, with players of all ranks, plenty of teaching rooms, tournaments, and weekly lectures by professionals. You can play with a downloadable client through a quick Java webstart, in your preferred Internet browser, or from your mobile phone.
The Internet Go Server - An older and more well-established server, IGS attracts mostly stronger players, and is playable through a client or telnet.
Dragon Go Server - For those who don't have the time to play a game all at once, DGS is a turn-based web system, similar to playing chess by mail.
While the three listed above are the most popular, there are countless other servers available. Please refer to the Sensei's Library page for a more comprehensive listing.
Books and Equipment
Our club has an extensive library of hundreds of books and magazines, both old and new. We have books for beginners, life & death compilations, and a whole lot more. Books are free to read in the club and many can be borrowed with a deposit. A few books can be purchased.
You can purchase equipment from any of the following retailers:
Games of Berkeley - Right downstairs from us, Games of Berkeley has some great Go books and equipment. On Mondays, we are represented at a table in the middle of their sales floor so new people can find out about Go. They also host Berkeley Campus Go Club's Thursday evening meetings in one of their basement game rooms.
Gamescape - One of the best Bay Area resources for Go and other games. There are stores located in San Francisco, Palo Alto, and San Rafael.
Most tournaments require a membership from the American Go Association (AGA). Once registered, you'll be able to track your progress and have an official rating. With your membership, you will receive regular newsletters with news, announcements, and commented games in SGF format. Membership will also show your support for Go in the US.