Okay, I didn’t see the reference books thing, my apologies. (Many of these will, you just edit stuff out)

http://www.bookyards.com/
http://librivox.org/ (Actually audio)
http://www.textbookrevolution.org/index.php/Main_Page
http://en.wikibooks.org/wiki/Main_Page
http://www.archive.org/details/education
http://ebookee.org/
http://www.ebooksonus.com/index.html
http://www.freetechbooks.com/
http://www.free-ed.net/free-ed/
http://www.thefreelibrary.com/
http://www.e-booksdirectory.com/