[Wikibooks](http://en.wikibooks.org) hosts user-written textbooks licensed under Creative Commons Attribution-ShareAlike, and is hosted by Wikimedia Foundation (the same non-profit that hosts Wikipedia and other [sister projects](http://en.wikipedia.org/wiki/Wikipedia:Sister_projects)). Books can be downloaded in printed form or [ordered online](http://en.wikipedia.org/wiki/Help:Books/Printed_books) from PediaPress (which WMF has a partnership with) or a third party.