My university subscribes to netlibrary. After reading your post, I decided that I should probably finally check it out. They have 3,407 publicly available books, and it looks like ~500 that my univ pays for which seem to be in ranges from health to public policy -- both big prof schools on campus.
The publicly available books seem to be just that -- and they even source Project Gutenberg for many of them.
I suppose that if your library doesn't subscribe to the materials you want, you're SOL. Maybe your local library coughs up for more than my university... Who knows?