CruiseControl is an extensible tool/framework for implementing ContinuousIntegration. A more mundane use of CruiseControl would be to run a standard nightly build, or to provide an interface to build on demand.
http://cruisecontrol.sourceforge.net
see also .net version: http://ccnet.thoughtworks.com/
Click or not on the cross-hatchy thing by the flower to go to the Top Level Cruise Control Wiki. Many many neat people watch it.
