I just discovered IronPython and this is one cool system. This is a Python implementation that targets the .NET Framework and Mono. I was especially interested to see this on the page:
Fast - IronPython-0.6 is up to 1.7x faster than Python-2.3 on the standard pystone benchmark. An early performance report is are contained in this paper for PyCon 2004.
I've only started playing with this, but it shows a lot of promise. I also noticed on Jason Zander's Weblog that Jim Hugunin, the author, has joined Microsoft.