NOTE (2006-05-07): I've just discovered Isotope which is a lot further along, so I might investigate that and abandon pyso.
pyso is a pygame-based isometric game library that I'm working on.
I've started off cleaning up Pyplace which is an existing library that doesn't seem to have been worked on since 2001.
You can download my initial effort at:
My next goal is to further extend this to a usable library.
The long-term goal is a platform for a wide range of sprite-based isometric games from Civ II-style turn-based strategy to city-management games like Caesar II