Instead of starting your own, why not contribute to Wikibooks? It's already an established site with a fair number of users, but there are several sections (especially technical areas) that are incomplete or haven't been updated in years. Plus, everyone else would be able to start contributing NOW.
Simple reason is that they don't achieve what I think is important - namely clear progressions and dependencies from topic to topic, and a high level overview, and more, I don't think they can be made to do that.
They are fantastic resources, and I hope people continue, or restart, work on them, but I think they are resources for the system I'm envisaging, not a replacement, or starting point.
http://en.wikibooks.org/wiki/Wikibooks:Mathematics_bookshelf
http://en.wikibooks.org/wiki/Wikibooks:Computer_science_book...