http://www.half.ebay.com/

eBay's little sibling, specializing in books, music, video and other media forms. Not an auction format, Half sells for fixed prices set by the seller. Most items used, some new. Shipping costs are added to price. I've found a wide range of prices on items, depending on the seller. Some great bargains to be had at pretty reasonable prices. Sure, you can get them cheaper at a yard sale, but not too many of them carry untold thousands of volumes. You can also get into the selling end of things pretty easily too. I haven't made a fortune on it, but have cleared out dozens of books and movies and converted them to cash.