Added my weblog to www.alphainventions.com yesterday because a friend told me he got a big spike in traffic as a result. It actually worked!
It's kind of interesting site. It rotates through blogs kind of like a jukebox or something and you can pause the "Play" if you want. Because people a) add their blog and b) sit there to see if/when their blog pops up, it adds visits to your blog if it's part of the played sites.
Interested to see if this results in just an uptick on one day or a consistent flow of traffic. Looks like there is a paid version which purports to deliver "100x" the traffic.