4,000 science titles from the National Academies Press (NAP) now available as free PDF's (really, legally, direct from NAP, but registration is required...)
"WASHINGTON -- As of today all PDF versions of books published by the National Academies Press will be downloadable to anyone free of charge. This includes a current catalog of more than 4,000 books plus future reports produced by the Press. The mission of the National Academies Press (NAP) -- publisher for the National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council -- is to disseminate the institutions' content as widely as possible while maintaining financial sustainability. ..."
4,000 titles... That's going to take a bit to read... :P