Tappx

Tappx is an online community that enables developers to promote their app for free by exchanging ads with other developers. You earn credits showing ads from other apps, and those credits are consumed when other apps promote yours.

Tappx is a cross-promotion community, made by developers for developers. It is designed to give mobile app developers a free platform to increase the popularity of their app during the launch in the app market. The website currently hosts a wide collection of apps developed by users from around the world.