If you’re interested in learning more about the game of Go, whether you’re an absolute beginner or already know something about the game, a good starting point is “Sensei’s Library”, a huge wiki (it currently contains 15722 pages) all about Go. There are many ways to explore the wiki, and tons of interesting topics to explore.
There are are many nice English language books on Go. I will just recommend, if you are a beginner, the excellent five volume “Learn to Play Go Series” by Janice Kim and Jeong Soo-hyun. (If you already know the rules and have played a couple games, you probably want to begin with volume 2).
Go-playing programs, unlike Chess programs, are no match for even moderately strong human amateurs, but for beginners or weak players like myself, they can provide an interesting challenge. I very much like the free Goban Go GUI for Mac OS X, which includes GNU Go, which is one of the best Go-playing programs. Goban also serves as a client for online Go servers and lets you replay Go games in the .sgf format.