I'm a developer and have one iOS app currently in the App Store and two more currently being reviewed for submission. I have the developing side of the project down, but am in dire need of marketing tips. I've come across sites online that claim to market your app for you. Does anyone have any experiences with sites like these? Also, sites like http://www.whatsoniphone.com/ sell ad space for your app. Anyone have any luck with sites like these? If so what sites have brought you success?