Not only is the css-discuss wiki full of useful information about CSS, it's one of the best-organized wikis I've seen. The home page is laid out like a topical table of contents, giving you a sense that this is more than just a pile of pages: there's some structure to it. Maybe it isn't really more than a pile of pages, and maybe other wikis have just as much internal structure. It's just that the maintainers of this wiki took the trouble to organize it for us.