Open Text books
Open source books:
http://en.wikibooks.org/wiki/Main_Page
http://www.opentextbook.org/
http://www.opensourcetext.org/
http://www.lightandmatter.com/area1book1.html
http://ocw.mit.edu/index.html
http://ocw.usu.edu/Index/index_html/ECIndexPage_view
http://ocw.jhsph.edu/
http://cnx.rice.edu/
http://sofia.fhda.edu/
http://www.cmu.edu/oli/
http://www.merlot.org/Home.po
http://nsdl.org/
from Mark Pilgrim on: nonstandard