I have been playing around with meteor, an open-source platform for building web apps. The result is a 200 LOC game ladder with a live demo.
The platform is built on top of nodejs, what is great. In my opinion, it is not ready for production environments yet, but I am really impressed with how fast you can create simple web applications with live page updates, automatic data synchronization and many other niceties I have never seen before in any other web framework.
ELO algorithm
There is an open issue with the ranking algorithm. I am looking for a javascript implementation of the ELO algorithm. I am waiting for your pull requests!