Mac Wiki Guide from MacRumors
Looks like MacRumors has a few more tricks up their sleeve (besides the obvious), as they've launched a wiki Guide to all things Apple and Mac. I don't know how this stacks up to the likes of the Wikitosh, but I've already learned a few things just browsing through, such as the old-school ADB port that offered an advantage or two over today's USB.
MacSlash, where I found this, notes that MacRumors isn't attempting to create some definitive encyclopedia. Instead, it sounds like they're just trying to organize the massive amount of information their forums seem to collect. I tip my hat to whoever had that crazy idea.