I have implemented Amazon CPM Ads to my other site http://mathtuition88.blogspot.sg/ which is currently mainly used to host my Javascript Apps like:
- LaTeX to WordPress Converter
- JC Ranking Score (UAS) Calculator
- NRIC Birthday Month Calculator (Fun App)
Revenue wise, Amazon CPM Ads beats WordAds hands down. Amazon CPM Ads pays at least 3 times the amount WordAds pays, for the same amount of traffic. It can also be integrated with Amazon Associates via the “passback” ad, so that when the CPM Ad is not filled, it shows the Amazon Associates affiliate ad instead.
For WordPress.com, the only form of ad allowed is WordAds, which is still in the development phase.