Free ebooks can also be found at Inkmesh ebook search engine
Inkmesh aggregates both non-copyrighted free-ebooks available at Gutenberg, ManyBooks etc. and also aggregates in-copyright promotional free ebooks from Amazon, BarnesandNoble, and Sony.
We are also continuously working on adding more such sites in our index.
Let us know if you want us to add any other sites that you find interesting.