WSPBuilder extensions for Visual Studio are great. If you use WSPBuilder to create webparts however, you might have run into the fact that by default Visual Studio does not allow you add Web User Controls to a WSPBuilder project.
At the project I'm currently working on, we use WSPBuilder and usercontrols for the visual part of the webparts we create. To make life a bit easier we altered the projectfile of our webparts project.
If you change:
Visual Studio wil think it is now a WebApplication, and will allow you to add usercontrols by using Add --> New Item on your WSPBuilder project.