Links and Downloads

D20 Systems

Ultimate SRD (hosted on this site): Fan-made collection with the goal of integrating all the D&D content.
Hypertext d20 SRD: Site with all OGL D&D content, including errata.
WotC sources: Official D&D FAQ; Official D&D Errata; Monster finder Incomplete but useful; WotC Master lists List of invocations, monsters, spells, feats, and character and prestige classes. Incomplete.
Misc: D&D product lists WOTC used to have this on their own website...; ~~d20 v3.5 Indexes (updated 06 Oct 2007) Nearly every 3.5 rule is cataloged in these PDF files, from Crystal Keep.~~WOTC pulled it; List of Prestige Classes on wikipedia

True20: True20 (hosted on this site); Forum
Mutants and Masterminds SRD
d20 Modern
d20 Threshold: A free d20-based, cross-genre, classless roleplaying game inspired by the 3rd and 4th editions of the Dungeons and Dragons games, the Pathfinder Roleplaying Game, and the Star Wars Saga d20 game and Mutants and Masterminds.

NPCs: NPC wiki abandoned by admin but lots of content; NPCs admin from previous has started posting NPCs here.
Names: For names, The Extraordinary Book of Names by Gygax is highly recommended.; More names; Index of Name Generators
Blogs: Gnome Stew

Bubblegum This game is a comic-bookish game where your character progressively gets better at kicking ass (and progressively worse at doing normal, mundane things.) The rules for this fit on one page.
John This game, which has two pages of rules, revolves around John. John is an average person with extreme schizophrenia. In this competitive RPG, everyone plays a different personality of John, vying for control of him and attempting to fulfill their own goals.
Fiasco Fiasco is inspired by cinematic tales of small time capers gone disastrously wrong -- inspired by films like Blood Simple, Fargo, The Way of the Gun, Burn After Reading, and A Simple Plan. You'll play ordinary people with powerful ambition and poor impulse control. There will be big dreams and flawed execution. It won't go well for them, to put it mildly, and in the end it will probably all go south in a glorious heap of jealousy, murder, and recrimination. Lives and reputations will be lost, painful wisdom will be gained, and if you are really lucky, your guy just might end up back where he started.