Instead of searching the Sony site, just go to
http://www.inkmesh.com/free-ebooks/. They do a pretty good job of cataloging freebies from across the bookstores. Most of the best finds are on Amazon, but it's easy to strip the DRM off of those. You just have to watch out for the promotional offers that only give you the first few chapters and the poorly written ones from SmashWords. I've downloaded close to 200 contemporary books over the last year.