Check out Baen Books (http://www.baenebooks.com/default.aspx) if you're into SF or Fantasy. They have a "Free Library" of books where (for example) the first one in a series is free so you can check it out. The big advantage of Baen is that their downloads are DRM free so you can download in any format (including Kindle) any number of times and use/read them on any machine with any software, rather than being locked in to a particular machine/software combination. Plus, as you'll see if you check out their prices, even their paid books are much cheaper.