gamification/rewards -- looking for projects/code to review

Hi,

Looking to possibly start a project which will have a rewards/badge kind of
logic/process for the users.

Rather than go from scratch, I'm curious to look over other free/open
source/demos. Looking at webapps.

Conducting the usual searches, and thought I'd ask here as well.

If you have pointers/comments, fire them my way!

thanks