With proper project settings, you can place your source anywhere. You are right, there's nothing documented about this approach and I'll give you a brief overview to try it out:

• Create a WAP project the usual way, inside desktop modules
• Configure the project URL setting to point to the desktopmodules/mymodule/ path (project properties). Properly setting this value will allow you to debug normally later on.
• Configure the application URL setting to point to the local development website (project properties).
• Move the folder to where you want it to reside.
• Fix the paths to the dll references
• Fix the project URL setting

Of course, you will need to copy the necessary files to the local development site. It's better to automate this (either nAnt or some MSBuild tasks).

AFAIR, Philip Beadle has used this in the template for DNN and TDD that he posted in Codeplex, you will probably find that this is the approach being used there.

Thanks for your answers!

Indeed, your solutions are ok. But I'm not happy at all  I hoped, there is a proper way withou any "hacks". Has anybod tryed out following solution?

haacked.com/archive/2006/02/07/AddingWebUserControlToAClassLibraryInVS.NET2005.aspx