Role-playing Games Links:

The Order of the Stick is the best ever stick-figure cartoon based on the D&D game!
Wizards of the Coast are the producer of Dungeons & Dragons, and they have a website with lots of good, free content.
Formerly Eric Noah's 3E site, this place has got it all! News, links, forums, and more.
Wanderer's WWW RPG page was a great source for material for many different types of games, but doesn't look like it's being actively maintained any longer.
Larry Elmore is one of the best fantasy artists out there, and he has lots of his art on his homepage.
Alien planet designer is a set of scripts that allow you to create your own star system. Useful for hard science fiction games.
This language generator page is a useful tool for DMs.
Claudio Pozas does a lot of fantasy art work. A lot of his stuff is good for monster or character counters or portraits.
The Creature Catalog has monsters both new and from previous editions of D&D, all converted to 3E rules.
This name generator is pretty cool - it generates names based on a Tolkien translation of your own name.
Reaper Miniatures is the company that creates my personal favorite line, Dark Heaven. You can view their catalogs online - fantasy, sci-fi, armies, and more!
This website has many spell and character record sheets for both D&D 3.0 and 3.5 editions.
This website has all kinds of graph paper for downloading.
Crystal Keep hosts a PDF 'Index of Feats' that draws feats from Dragon Magazine, official WotC rulebooks, and even web enhancements (!) into one source document. Extremely useful!
The D&D 3.5 System Reference Document, an online copy of the game's core rulebooks.
The Pathfinder System Reference Document, an online copy of the game's core rulebooks.