tapioca-sharp
tapioca-sharp is a .NET package containing high-level classes on top of TelepathySharp for use in clients. It's used in at least landell.
Development branch
The current version is in svn: svn co https://svn.sourceforge.net/svnroot/tapioca-voip/trunk/tapioca-sharp
More info can be found at http://tapioca-voip.sourceforge.net/wiki