I started looking at creating a port of the cctray tool for CruiseControl.NET but after looking at how it was implemented i decided that it might be easier, and more fun, to implement one myself using mono and GTK#. At the moment the application has the ability to display notification when a build event occurs and to display the list of projects that are being watched. The source code will be available on Launch Pad when I figure out how to use bzr.
here are some screen shots of how it currently looks.
Cruise Control.NET home page