Have you tried Airpush? We are the largest Android only ad network.
We have free plugins for Adobe Flex, and other platforms. You can see our list here:
manage.airpush.com/docs/index.php?title=Plugins_for_Airpush_Android_SDK
Our newest SDK pays includes a pay per install where you can earn up to $0.04 per USA user install and opt in, in addition to display advertising revenue.