Amazon has a great selection of “free classics and out-of-copyright, pre-1923 books, as well as limited-time free promotional books” on their Free Book Collections page in their Kindle Store. If you don’t own a Kindle, no problem. You can also read the books for free on your iPhone/iPod Touch, Windows PC, Mac, BlackBerry, iPad or Android.
The Free Book Collections page also has instructions for downloading free titles from a whole host of other sites online offering pre-1923 books.
Find more free ebooks here.