One great place for free ebooks is Project Gutenburg. They make available free books in the United States because their copywrite's have expired. Completely legal (in the US) and there are some cool classics there.
I like going to http://www.kobobooks.com where they have a "free" ebook section that has a very nice selection to choose from. I have downloaded and enjoyed reading such classics as "The Adventures of Sherlock Holmes" and "A Tale of Two Cities".
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