This is the short and simple version of my guide on how to learn Go. If you really want the novel-length version, I’ve linked to it at the end of this guide.
• The Interactive Way To Go introduces the rules of the game and basic tactics. It’s great if you’ve never played before or just played a handful of games.
• I recommend playing 9×9 games to learn tactics. It really helps you focus, and learn the essential part of the game: fighting.
• The KGS go server is friendly and a good place for both beginners and experienced players. Look for the beginners room and the kgs teaching ladder.
• Computer opponents can be convenient, even though you can learn more by playing other people. Igowin is the easiest to install and get started playing (windows, iPhone). Or you can look at GnuGo (cross-platform).
• There are clubs all over the country. Most clubs welcome players at any level of strength and interest. You can find them either via the American Go Association website, or Igolocal, a new service for finding face to face opponents.
If, after playing for awhile, you want to learn more in depth about the strategy of the game, I have some suggestions.