====== Ad buying management and aggregation ======

  * http://www.invitemedia.com/
  * http://adbuyer.com/
  * http://www.openx.org/market

===== PPC =====

  * http://www.clickable.com/

===== Yield optimization =====

  * AdCamo http://www.adcamo.com/
  * AdMeld http://www.admeld.com/
  * LiveRail Junction http://www.liverail.com/junction.php 
  * PubMatic http://www.pubmatic.com/
  * Rubicon Project http://www.rubiconproject.com/
  * Smaato http://www.smaato.com/