John Roth, the PyFit developer/maintainer, finally uploaded the latest version of PyFit to the CheeseShop. PyFit is the Python port of the FIT framework initially created by Ward Cunningham. PyFit also integrates with the FitNesse framework, so you get the best of both worlds. I wrote a series of PyFit/FitNesse tutorials which you can read here.
I'm currently writing PyFit functional/acceptance tests for the application that Titus and I will present at our PyCon tutorial. Writing acceptance tests as Wiki pages peppered with test tables is a very effective way of both documenting the desired behavior of the software and testing it at the same time. The FitNesse tests serve as an alternative GUI into the application. They test it at the "business logic" layer, which means that they are much more robust in the presence of GUI changes. See this post of mine for some thoughts on running FitNesse vs. Selenium tests. For a great series of articles on Agile Requirements and Fit-syle testing, see this post from James Shore.