TestDriven.NET is one of my favorite add-in for Visual Studio for unit testing. Normally I used NUnit or MbUnit for my unit testing. Recently I was trying on xUnit.net which is still not supported by TestDriven.NET yet. However, it has a a TestDriven.net 2.x test runner (inside Visual Studio) which you can use.
I am not going into details here, as you can find an interesting article on it from the website.