I've been thinking a bit more about kitchen-sink d20. Even though the term "kitchen-sink" likely conjures up visions of carte blanche, even the most permissive game needs a few safeguards. As always with GMing, a lot of trouble can be avoided by a give-and-take of expectations before the kickoff of a campaign. Here's my rules thus far:
-Max level adjustment of +2 for any race chosen.
-Nothing purposefully game-breaking (if you found out on the Character Optimization boards at Wizards of the Coast this amazing combination granting you 500 1st-level hit points, don't do it). As a guideline, feel free to do something different, but respect the game. If in doubt, ask!
-Players must own the book or (legal) pdf in order to use a race, class, or spell. My collection, the collection of other players (with their permission), and approved online resources (such as the Grand OGL Wiki and Netbook of Feats) are also allowed.
-AS GM, I reserve the right to deny any build or character option if I feel it would not be in the best interest of the game, but intend to be pretty liberal in this regard.
Those are my basic thoughts on it. I don't want to go too far with this, as I'm fortunate that I believe I can trust my own group with pretty simple guidelines. If anyone else has any input, I'd be glad to see it!