Unlike Internet Archive, Project Gutenberg finds books from all publication dates and lets you download them for free at almost any format for any device (iPad, Kindle, Sony Reader, iPhone, Android). There books are 100% legal and free because they let you download books that are out of copyright in the United States. With their partners they have over 100,000 books. Great site, it even has banned books if that interests you and more. So before you purchase a rare/unique book online check this site if it has it. Click on the link below to get to Project Gutenberg.
Ever wanted to check out how Google looked in the 90’s or how Facebook looked when it first came out? With the Wayback Machine you can, it has 56 billion captures of over 10 billion web pages dating as far back as 1996. It’s a non-profit website which was created by the Internet Archive. Here is the link below. Have fun!