Cassini V2 with source code available
Dmitry published V2 sources for the Cassini web-server a few weeks ago at: http://blogs.msdn.com/dmitryr/archive/2005/09/27/474534.aspx
It is worth checking out if you want to see the new ASP.NET 2.0 hosting APIs in action, as well as how to build a web-server that hosts ASP.NET.