Chronos is a project mainly written in RUBY and JAVASCRIPT, it's free.
What do you think about manage a software project based on acceptance tests? That's what we are doing!
Every software project can be broken into a bunch of features (User Stories), which in turn can be broken into a set of scenarios.
The smallest piece of software that a team could be working on, and the client could understand is the scenarios.
The Cucumber acceptance test framework