I know everyone is fully capable of using goggle or some other search engine to look for e-books, but I am a big advocator of "one stop shopping", The link below will take you to a site that has, no exaggeration, over 100 links to sites that offer e-books in numerous formats, subject matter and in more countries than you would believe that have this resource. Name a subject and you will in all probability find a link and an E-book, most are free and public domain but many are of more esoteric subjects. Many of the books that are being offered for free from other sites are listed here. Hope this is a helpful resource for those that have a need.
Merry Christmas
http://www.e-book.com.au/freebooks.htm#4