Other Fun Websites

Math resources are now collected seperately as resources for research and resources for students.

The Interactive Fiction Archive, the Great Library of IF. Most of what is worth knowing about IF is here, somewhere. On the other hand, unless you're looking for something in particular, you'll be better served by...
Baf's Guide to the Interactive Fiction Archive, which catalogs the games at the archive by genre, development system, quality, and a host of other details. Reviews are available for some games.
XYZZYnews and the Society for the Promotion of Adventure Games are two organizations which publish news for the IF Community, including reviews, interviews with authors, and development and design articles.
The Annual Interactive Fiction Competition is probably the biggest event of the year for the interactive fiction community, and produces a wide variety of games. Some of the best games of the modern era of IF are actually IF-Comp entries.
The Interactive Fiction Wiki triues very hard to collect in one place all knowledge about interactive fiction in the known universe. Like most wikis, it's chock-full of information of varying levels of accuracy.

BrettSpielWelt is an impressively detailed online board-gaming site with all of the favorites of the twinkie crowd. It's mostly German-speaking and not everything attached to it is translated, but, mmm, free online gaming.
The ifMUD is mostly a glorified chat-room, and it's not just for IF any more (if indeed it ever was).
John Allison's Scary-Go-Round is the most delightful webcomic out there, in my opinion. Jeffrey Rowland's Wigu is also very cute.
Darkstar is the UCSD science fiction and board-gaming society. There's a bit too little actual board-gaming for my tastes, but maybe this year we can get events together. They've also got a fairly impressive library.
The Kingdom of Loathing is a very silly, free MORPG.