To be frank, the idea that one could ever get a thorough grounding in any serious, empirical scientific discipline by scouring the Internet is, at least at this time, laughable.
Is this because of the lack of lab work as well as the lack of textbook-level information?
Cognitive psych is ovbiously important to people here, so I want to point out a CogSci book thread over from reddit/r/cogsci.
http://www.reddit.com/r/cogsci/comments/bmbaq/dear_rcogsci_lets_construct_a_musthave_library_of/
I would be interested in an extension of this thread here, since LW has somewhat more computational theory of mind slant.