Here at TDPG we do TDD, so we have a huge amount of tests for our products.
When the project I’m working on started, about 1 and a half years ago, we were using MbUnit and Rhino Mock. After few months with Rhino, we decided to migrate to Moq, because of the nicer syntax, easy of use and better error messages.
As .NET developers, one of the tools we use all the time is ReSharper, it’s a wonderful product that help with TDD, makes refactoring super easy, and overall increment our productivity a lot.
To support our Agile Development process and TDD development, we set up a CI (http://bit.ly/KEgGa) platform