I just recently played with CruiseControl.NET and decided to use it in future releases [ starting in two weeks..maybe sooner] for Rainbow Portal 2.0.  Long story short, CCNET allows for agile integration development and is prime for open source projects.  I posted a blog entry on GWB on my plans to use it with rainbow and a description of some of the features.  The CCtray component, which is free for download, allows you to point to any CCNET server.  This translates [ for Rainbow] the ablitiy to send notifications out to anyone would like information on the build status [ new, broken, up] via the windows system tray [sorta like google alerts].  The beauty of this is that its all open source :).  In conclusion, CCNET would make a great addition as a Rainbow Module.

Here is a screenshot of my first build of rainbow: