The Open Geospatial Consortium has developed many standards for Web Map Services used for exchanging geographical data. One of this standard is Web Processing Service, defined in OGC 05-007r4 draft document.
PyWPS has been started on Mai 2006 as project supported by DBU. It offers you environment for programming your own process (geo-funktionality) which you would like to server to the public. The main advantage of PyWPS is, that it has been written with native support for GIS GRASS. Access GRASS modules via web interace should be as easy as possible.
PyWPS is written in Python.