You can use an ad provider such as AdMob or Mobclix, and integration into your app is pretty straightforward. Some services also support dynamic allocation bet

You can use an ad provider such as AdMob or Mobclix, and integration into your app is pretty straightforward. Some services also support dynamic allocation between multiple ad networks. This is useful if you want a higher-paying ad network to serve ads most of the time, and defer to other networks if an ad is not available. Mobclix supports this, as well as the AdWhirl library.