With particular note for free applications that need to increase their “stickyness” to achieve reasonable revenues via in application advertisements such as those provided by Admob, adding community features such as a high score boards and messaging between users.
http://corporate.scoreloop.com/
Provides location aware global high score boards
Ability to post to notifications to Facebook
Issue player challenges
Cross promotion of other games in the score loop system
Example game Wild Solitaire http://linktoapp.com/wild+solitaire
Compare games with friends
Location based scoreboards
game profiles
Achievements
Example game: http://linktoapp.com/alex+the+fox
Plus Plus is NGMocos private version of the above tools, they do intend to make it open in the future however
Example game: http://linktoapp.com/eliminate