hey check out this app http://appsforfree.net/freebie
The link to appsforfree.net/freebie redirects to a page from EverBadge. The offers on this page are an example of gamification.
EverBadge was formerly a social network aimed at and used by mobile online gamers. After reaching a quarter million registered users, it began to attract more attention from mobile app advertisers and developers.
Eventually the gaming social network side of EverBadge disappeared entirely and the company began fully focusing on Android app ad serving and gamification.
Ad serving is the system of maintaining, improving and customizing online advertisements. An example of this would be searching a website for engine oil and along with the search results the user would also see an ad for oil filters or additives. It is ad serving technology that connects customers to the ads that theoretically most interest them.
Gamification is the effort of improving the online experience by adding game-like aspects to an otherwise non-game-like task. An example of this can be easily found in many discussion forums. If a forum member is awarded points or titles (Guest, Senior Member, All-Star, etc.) for providing a certain number of answers or contributing substantive posts, they are more likely to participate.