I've started reverse-engineering and documenting the wallet and block databases, and have written some Python code that deserializes many of the Bitcoin data structures. I was going to let it ferment a little more before announcing, but Mr. Google will surely find and index it soon, and it should be a good head start for anybody who wants to start a Python bitcoin client.
Open source, MIT license, at:
https://code.google.com/p/bitcointools/ MOVED TO git:
http://github.com/gavinandresen/bitcointools