VSNUnit

VSNUnit is a very useful NUnit related tool. It integrates NUnit into the VS environment and makes unit testing activities in VS easier and faster - you do not have to leave the working environment while testing. The developer receives test results integrated with his source code.
I really like it. There are some problems that should be fixed / it's beta3, yet / , but anyway I like the idea.
The tool is open source and may be obtained from here