Unit testing made easy
Unit testing has taken a new momentum with the rise of the agile development practices. NUnit is a fantastic and simple unit-testing framework for all .Net languages but if you used it before you have probably come across the difficulty on how to isolate the unit that you want to test. NMock was created to address this issue. Mock Objects to the Rescue is a very good article on how to use this useful tool.
If you have not used NUnit before you will find a good introduction on the Test Driven C# msdn article.