There are several projects to produce OA textbooks, and lots of individual OA textbooks around the web, but Textbook Revolution is the first portal and comprehensive collection OA textbooks that I've seen. (Thanks to LIS News.) You can browse the collection by discipline, search it by keyword, or subscribe to its Atom or RSS feed to track new additions. From the site:
In response to the textbook industry’s constant drive to maximize profits instead of educational value, I have started this collection of the existing free textbooks and educational tools available online. This website has several reasons for being: [1] To serve as a catalog of resources for students and teachers looking for free textbooks (one-stop shopping), [2] To act as a mirror for files. Mirrors help reduce bandwidth costs and prevent files from disappearing if a website goes out of business, [3] To promote the need for and availability of free textbooks.
Posted by
Peter Suber at 11/29/2005 08:47:00 AM.
The open access movement:
Putting peer-reviewed scientific and scholarly literature
on the internet. Making it available free of charge and
free of most copyright and licensing restrictions.
Removing the barriers to serious research.
I recommend the OA tracking project (OATP) as the best way to stay on top of new OA developments. You can read the OATP feed on a blog-like web page or subscribe to it by RSS, email, or Twitter. You can also help build the feed by tagging new developments you encounter.