There are a number of websites that can provide access to e-books for free. Here are some of the better-known ones:

InkMesh - searches over 30 online sources for free e-books. (http://inkmesh.com)

Project Gutenberg - mostly classic and public domain books. (http://www.gutenberg.org)

Baen Books - for science fiction and fantasy. (http://www.baen.com/library)

Feedbooks - public domain books but also original works. (http://www.feedbooks.com)

Internet Archive - good for lots of media on the Internet including e-books! (http://www.archive.org)

Open Books Calibre - has free ebook conversion software and a collection of free DRM-free ebooks
(http://drmfree.calibre-ebook.com/)

epubBooks - all free! (http://www.epubbooks.com/)

Kindle World blog - links to low cost and free Kindle books. Links to Amazon. (http://kindleworld.blogspot.com/)