NCrunch provides continuous testing for Visual Studio. When I make any change to my code which breaks a unit test, the NCrunch risk status goes red a few seconds later, even without recompiling. I get immediate feedback for any breaking change, so long as I have a test for it. Not only does it encourages me and my team to write good tests, but it allows us to make new changes and refactor with confidence.
Redgate .NET Reflector Developer Bundle
Also, while there are several good .NET decompilers, many of them free, I got used to .NET Reflector which comes part of this bundle.
For a more advanced use case, see my post about automatically converting DevExpress v1 report scripts to check for compilation errors and allow for unit testing of report scripts.
I always install the Amazon Web Services Toolkit to make it easy to spin up test servers in the Amazon cloud.