In all seriousness, no one should really use this. There are really good tools out there for managing a budget, but I like to write my own tools.
This is a simple three tier application that provides a web front-end to a budget database. The first version was a standalone app that was written in a pinch during tax time a few years back. Since then I started re-writing this as a drupal module leveraging the views 2.x API, the FAPI ahah interface, and jQuery. These attempts were abandoned in favor of the cake PHP framework which is capable of serving the application in a more standalone fashion.