Clever Harold is a new python web framework (another one :-) that uses WSGI as its core glue. This allows you to define your own stack of elements (sessions, authentications, compression, templates, etc.).
It is really well done (for a 0.1 version), and, compared to other WSGI based frameworks (like RhubarbTart or Pylons), seems easier to grasp. The big difference (except it’s well organized, thanks to Paste) is that it automatically guesses the required modules, so you don’t need to specify them in your source header.
Take a look at it, and don’t forget to register on the mailing list!