WPS implementation - PyWPS.

That's actually the first implementation of WPS I've found out, which is heard of from ka-map-users mailing list.
PyWPS was started on May 2006, written in Python, based on GRASS. It allows users to publish their own geo-processes which should also be programmed in Python.
And, there's Ajax UI for PyWPS as well, Embrio & WUIW.