CLPython - an implementation of Python in Common Lisp. Simply because it combines two of my favorite languages and makes pure-Python libraries available for Common Lisp. Perhaps now some of you can see where my search is heading - to have my cake and eat it too. By the way, CLPython is compatible with Python 2.5, so it's even a fairly up-to-date language level (even though I'm sure I'll miss some things from 2.6, but it's no different with PyPy).