Ok, after seeing a few posts here and looking extensively for online PDF books and textbooks for a couple days, I found an AMAZING site that has nearly every book you could ever ask for. I'm not kidding.
www.avaxhome.org
I found hundreds and hundreds of books here, from very recent popular authors to textbooks on any subject you can think of. This site is really amazing. Just go there, click on "ebooks" up at the top, and search for anything you want on the left side column. I downloaded probably about 200 different biology, physics, chemistry, technology, and a few other types of books in the first few hours of finding this site. You might want to get a short subscription to rapidshare.com (only a few dollars for all the amazing books) and you can download a bunch at the same time.
Anyways, I figured I'd make a nice little contribution to the the ever expanding knowledge of the ImmInst members for my first post. Have fun.