From GISWiki

Chameleon is a distributed, highly configurable, environment for developing Web Mapping applications. It is built on MapServer as the core mapping engine and works with all MapServer supported data formats through a regular MAP file. It also works well with OpenGIS Consortium standards for Web Mapping Services (WMS) and WMT Viewer Contexts through MapServer's support for these standards.

Homepage

http://chameleon.maptools.org/index.phtml