I've added a Project Wonderful ad to the sidebar. I'm not doing this to make any kind of significant money. Most sites with my traffic might get a penny a day in advertising if they're lucky. I'm doing an experiment to see how Project Wonderful works, both as a publisher and as an advertiser. Advertising will come later. I have a few projects I'm working on that I'll advertise as they mature.
There are two main reasons I'm trying Project Wonderful: funds are usable, and the system is more community oriented than other advertising networks that I've looked at.