A couple of weeks ago, AdWords launched Site-Targeting, a new type of campaign that will work on a CPM (Cost/thousand impressions) basis, on their Content network. While this might be a great tool to promote brand awareness, the CPC (Cost/click) seems to remain the best model for campaigns that aim to generate direct online sales, rather than awareness.
This option will only be available for the new campaigns created after having turned Site-Targeting on, in the account preferences.