Carnegie Mellon University has partnered with many libraries accross the globe (and the ubiquitous Google) to digitize and make available over 1.5 million books online.
This is the largest repository of digital books around! Now you too can read the library whever you are, as long as you have access to the internet. The eventual goal is to digitize all books in print, athough copyright law is causing an obvious hinderance. At the moment, the only books included are those whose copyright has run out, or whose authors and owners allowed the project to digitize their works. Read and love!