The Palm Pre application store has about 400 applications. Many are paid and some of them are free. The free ones need a way to make money so this is where AdMob comes in. AdMob announced today that they are providing beta support for placing advertisements within Palm applications.
As you may remember Google announced to buy out AdMob for $750 million in stock about a month ago.
So far AdMob offers only one ad unit which can be placed within an application. The ad unit can be a CPC text based ad or a CPM banner ad.