Take a look at the CCCmd command line tool:
CruiseControl.Net Command-Line Utility
Provides command-line access to a CruiseControl.Net server
CCCmd <command> [options]
command: one of the following actions
help: display this help screen
retrieve: retrieve details on a project or server
forcebuild: forces a build on a project
abortbuild: aborts a build on a project
startproject: starts a project integrator
stopproject: stops a project integrator