Anyone know where to find College Textbooks on pdf?

Since we have a lot of intelligent people here, I thought someone might know where to find pdfs for college textbooks. I already tried all the BT and RS search sites (if you don't know, don't ask :P). Chances are, if you can find it on google, I would have found it already. I'm asking if anyone knows a more...secret place.  

I don't know anything about torrents...I've been lucky enough to find some free nonstandard analysis books a while ago but that's it...textbooks I usually think of as necessary pain...but I love them once I have them!

I don't what RS is but demonoid is ok.

You can't register for Demonoid right now as the registration is closed. Try 4shared.com though I know it won't help u find what u need.