Tufts OpenCourseWare is part of a new educational movement initiated by MIT that provides free access to course content for everyone online. Tufts' course offerings demonstrate the University's strength in the life sciences in addition to its multidisciplinary approach, international perspective and underlying ethic of service to its local, national and international communities.
The Assayer is the web's largest catalog of books whose authors have made them available for free. Users can also submit reviews. The site has been around since 2000, and is a particularly good place to find free books about math, science, and computers. If you're looking for old books that have fallen into the public domain, you're more likely to find what you want at Project Gutenberg.