This thread is a compilation of stuff I like, stuff I've made, and stuff that is helpful, due to the signature restrictions. If there is any resource I have missed in the help section, please feel free to alert me.
SRD: A place to find the OGL core referrence books (PHB, DMG, MMI, XPH, ELH, and UA). It has most of the rules in those six books, aside from the actual text (fluff and such) and a few monsters (Poor illithids and Thri-Kreen).
Brilliant Gameologists: The new CO. A place to find help with everything character related, as well as all the handbooks you could ever want. Eventually, anyways.
X stat to Y bonus: This thread is being costantly updated, and has most all ways to get that one stat added to that one bonus.
Lists of Stuff: One of the most useful threads for character building. This thread has ways to get almost every ability, like evasion, uncanny dodge, blindsight, and sneak attack progression.
Consolidated Lists Archive: A search section of Wizards that lets you find where that one class was.
Crystal Keep: Another search function, CK is more complete in some areas than the Consolidated Lists Archive, but less complete in some.
Realms Help: Need a feat? Search here. Almost every feat in 3.x can be found here.
Dictionary of Terms (WotC version): What's Pun-Pun? This answer all of your online term questions.
Dictionary of Terms (GitP version): The GitP version, with some different definitions, and some that are not used on the WotC boards.
How to code: well, it's all the coding abbreviations for GitP.
How to Code: How to code for WotC forums.
Guide to Homebrewing: Need help getting started on your first homebrew? Start here.
Guide to Homebrewing (BG): The Brilliant Gameologists version of Guide to Homebrewing. Due to the small differences in coding, gotta put up both. See this one for templates for everything.
On the Philosophy of Class Design: Building a class or PrC? read this first!
Surreal's Handy CO guide: This has...lotsa stuff. Just go look at it. It's got some of the best CO builds ever made, the guide to optimization, how tos, you name it.
The Handbook Forum This is the subforum that has all of the handbooks made on BG. I'm pretty sure it's got everything that's been made on WotC, but if not, it will come shortly.
My General Houserules
Magic of Dmanum
Cleric of Sin
Cleric of Virtue
Anklets of Swift Flying
Goggles of Darksight
Two Marshal feats
My Houserules This is where I keep links to the classes I use instead of normal classes, as well as the things I have found to work well in my games. not everything yet.
My favorite things:
The BG Homebrew Arena: A way for you to test your creations in actual play, we allow the use of homebrewed content, as long as it is cleared by me or the other homebrew checking judges.
The Vorpal Tribble's Creation Thread: All of the creations of one of my favorite creators.
The Vorpal Tribble Monstravaganza: The monsters of one of my favorite creators: The Vorpal Tribble.
The Cat Burglar: A class about cats. And the people who turn into them.
The Avatar Project
The Falling Star Path: the Tenth Path of the Sublime Way: a collaborative effort headed by Tempest Stormwind including the marshal and ranger variants.
Comming soon! More stuff! As soon as I can find it.