If you ever wanted to implement leaderboards into your game, check out TurboScores: http://scores.turbomask.com/.
This is a simple, cross-platform and free solution for small games. API is based on REST, so you can use it almost everywhere. You can choose what security level to have, whether to use secret game keys or not. Our server side is greatly optimized, so all requests are processed as fast as possible.
TurboScores is in early beta right now and further development depends on user feedback, so feel free to contact us if you have any questions or suggestions.