Hands down CPA Lead is my biggest money earner because of all the possibilities that it brings. There is no doubt that you will have to have more then one site to really make any money but one of my lazier (no interaction needed sites) is this one here.
You can at least get a good idea how it works and then hopefully come up with some good uses for the interface. As I learn more I will display a bunch of URL's I have been using in conjunction with the software, not to mention it's sick fun!
The FTB Bloggers