Stats is a project mainly written in ..., it's free.
Node.js + mongodb based stats collection and graphing tool based on statsd from etsy
This is a simple statistics collection and reporting server I hacked up with node.js and mongodb. It's heavily influenced by the StatsD project by Etsy (https://github.com/etsy/statsd). I decided to code this since I wanted a backend that I could control better (MongoDB vs Graphite). Feel free to fork and hack away.