If you visit the blogs of Jeff Smith and Mladen Prajdić you'll notice they are now running the same ads as the main site. They were both running generic Google ads prior to this. We were able to tweak a SubText skin in order to pull ads from my ad server. The biggest benefit is that their revenue more than tripled and their ads are better targeted at their readers.
This is a companion discussion topic for the original entry at http://billg.sqlteam.com/2007/08/08/blog-at-sqlteam--earn-some-cash/