[johnward]

I don't the the answer to your question, but here is a pretty crappy graphic of some gaming networks I have bought traffic r

Here are a couple bookmarks I had that might work:

  http://cpmstar.com/
  http://www.ad4game.com/
  http://www.epicgameads.com/
  http://www.adengage.com/
  http://www.ad2games.com/
  http://www.inviziads.com/
  http://www.advertisegame.com/
  http://www.game-advertising-online.com/
  http://adsense.blogspot.com/2008/10/get-in-game-with-adsense-for-games.html