I love this kind of site. Not that you can't scour up the content yourself using Google, but here's the thing... when you're trying to "teach yourself" something complex, one of the challenges you run into (in my experience) is understanding the order of the dependencies for prerequisites and sub-topics. And nothing is more frustrating than trying to read a book or a paper and feeling totally lost because you're missing something that you should have learned first, but you don't even know exactly what the "something" is. :-(

As someone who considers himself something of an autodidact and who is always trying to learn new stuff, I really appreciate a resource that can point at a bunch of stuff and say (even in an approximate sense) "do this in this order". It really does make a difference.

Bingo. This is in complete contrast to visiting wikipedia where, for example, if I go to any mathematical concept, I seem to tumble down a series of holes that usually falls out somewhere much more abstract that what I need (usually topology). This is not to say topology is not important, but clearly becoming an expert topologist before learning wavelets (for example) would not be the most efficient way to learn the latter.