http://manybooks.net/ - currently 23,066 ebooks, mostly classics but not all, in these formats: app, azw, pdf, custom pdf, prc, mobi, pdb, isilo, ztxt, lrf, html, rtf, tcr, jar, epub, iphone bookmarklet, newton, ipod notes, custom html, lit, fb2, online reader. All free.
http://finding-free-ebooks.blogspot.com/ - listing links mostly to modern novel-length fiction. Various formats, depends on the provider. Book descriptions included. All free.