This app is a product whose initial engineering I have made open source. In fact, you can see this code in action at Running Balance OSS on Heroku.
This app is meant to evolve into some lightweight way to keep track of how much money you have in various bank accounts. It will also, at some point, feature a mobile version (some of the infrastructure for which I have laid down already).
Parts of this application have been open-sourced, for portfolio reasons. However, as development of this app progresses, further progress on the project may not be open sourced.
This is a normal Rails 3 app. bundle install etc etc is your friend
The website has good about documentation