One of the sites I follow religiously has the peculiar name of Books on the Knob. Its subtitle is "Bargain reads, book reviews, the Amazon Kindle and some games, technology and computers tossed in now and then." In spite of the subtitle, they actually list non-Kindle ebooks as well. Also, in addition to free books, they list discounted books. For example, Neil Gaiman's short story collection Fragile Things was available for 99 cents on Kindle; I was able to snap it up because I saw the post about it.
Books on the Knob (BotK) also lists games that can be downloaded for free or cheaply. I admit I don't pay much attention to them, but if you do, have at it. Also remember that Kindle books can be purchased (or downloaded for free, when applicable) through a Kindle for PC, Mac, iPhone or Blackberry app. You don't need to own a Kindle to take advantage of these books. BotK has links to access Amazon's list of all free ebooks, sorted into public domain and non-public domain.
Predictably, a lot of the free books are romance books; romance publishers were pioneers of digital publishing. Interestingly, many are from Christian publishers. The BotK post always alerts you to the publisher so you're aware of what you're getting. A lot of the posts are about books that are promotional in nature so the free or reduced price level is often temporary. If you're at all interested, I recommended adding this site to your own feed reader and keeping an eye out for books you might like. I actually really like seeing the reduced price books because those are ones the authors still get some revenue from. Free is nice, but authors have to eat.
The name of the BotK blog always intrigued me. I know of a slang meaning for knob, but I have difficulty making it relate to ebooks. -) I had no luck searching for the etymology of the phrase on the web. Does anyone out there know of a use for this term that makes sense in this context?