MapServer
MapServer is an Open Source platform for publishing spatial data and interactive mapping applications to the web. Originally developed in the mid-1990’s at the University of Minnesota, MapServer is released under an MIT-style license, and runs on all major platforms (Windows, Linux, Mac OS X). MapServer is not a full-featured GIS system, nor does it aspire to be.
The MapServer Project Steering Committee (PSC), sanctioned by OSGeo, manages and administers the project which is maintained, improved, and supported by developers and users from around the world. See the community activities page for mailing lists, etc.