I have used 3 PPC companies so far, Google Adwords, Overture, and Adbrite.
So far, I have had good returns from Google Adwords and Adbrite. My foray into Overture ads did not yield many visitors.
Adbrite is a bit different since the cost is based on site performance rather than keyword selection. In addition, unlike Google or Overture, you have the ability to select which sites you want to advertise on. In addition, Adbrite shows you how the site is performing for click throughs as well as total views.
If you have used any other PPC companies, please reply and describe your experiences.
MSN has a program that is also in beta right now too. I am not using it, but others have been using it. It only works with MSN search results, I believe.
