Rubydeps is a tool that uses graphviz to show a dependency graph of your project classes based on its tests. I think this is more useful than static analysis of the code base because of the high dynamic aspects of the language.

The main changes in this version are:
- Support for Ruby 1.9.x (no longer supports 1.8)
- Let's you dump test runs to a file so you don't need to start all over again just to change some filters

gem install rubydeps --pre

It works by running your test suite to record the call graph of your project and uses it to create a directed graph showing the class dependencies. Check it out!