There's a few scoreboard APIs out there if you look around. Also, I saw another post asking about Highscores and someone mentioned Clay.io. I've never used it but they developed a plugin specifically for C2 that comes with much more then just scoreboards:
[quote:3k8oje77]Achievements
Data Storage
In-game Payments
Analytics
Social Integration
Facebook posting & inviting
Tweeting
Posting to Clay.io Stream
Screenshots
Multiplayer Rooms
Cross-promotion
Ratings
Here's the link: [quote:3k8oje77]http://clay.io/docs/construct2