If you're into text adventures (ahem, Interactive Fiction), check out:
http://www.brasslantern.org/ - Lots of info, good beginners' guide
http://www.ifcomp.org/ - Annual competition for new works
http://www.ifarchive.org/ - Massive archive of most non-commercial works
http://wurb.com/if/ - Guide to the archive, reviews, listings
Also, if you read newsgroups, check out rec.games.int-fiction and rec.arts.int-fiction
EDIT: Also, the Zork games were released to the public domain by Activision when they bought the remains of Infocom several years ago. You can download them from:
http://www.infocom-if.org/downloads/downloads.html, among other places.