Maybe it's just an optimistic dream of mine, but so many people offer up great books on here, and there are so many great programmers that I would love to see a cumulation of the knowledge in an "open source" book.
Maybe it'd work the same way as this site does with users of certain reputation able to make new chapters, edit/add to the chapters, submit their own examples of code. If something is "downvoted" enough in some way, then it will be deleted. Either that or just edited by another user.
I don't know, just something I was thinking about recently. What do you guys think?