I installed an updated version of the NUnit VS add-in (aka: TestDriven.Net) today and discovered this little tool called NCoverExplorer. Curious, I started to dig into it and that lead me to NCover. NCoverExplorer is a GUI interface to NCover output files.
What is NCover? It generates code coverage information when it runs your NUnit tests so that you can see how much of your code base your tests are really touching (I perfer the output from Cenqua's Clover.Net, but I guess that's just a matter of using a better XSL transform?).
Both are great tools and should work their way into your development cycle!
It helps to have a simple batch file to run it:
"C:\Program Files\NCover\NCover.Console" "C:\Program Files\NUnit-Net-2.0 2.2.7\bin\nunit-console.exe" "..\bin\debug\SomeProject.Tests.dll"
In an automated environment, you'll want to take out the PAUSE. It's only there so that if you're running it manually, you can watch the result of the run.