If you haven't heard the news yet, Visual Studio Unit Testing, which was only available in some Team System products in Visual Studio 2005, will be available in the Professional Edition of Visual Studio code name "Orcas".
See this post from Naysawn Naderi for the details:
Due to popular demand we have decided to add the majority of the unit testing features of Team System to the Pro Sku of Visual Studio. With the release of Orcas, the support for authoring, generating and running unit tests, will become available to the users of the Pro Sku of Visual Studio. Pro customers will also take advantage of the some of the unit testing improvements we have added into Orcas, specifically generating for generics, performance improvements, the ability to unit test devices and better IDE integration (I’ll try my best to blog on the details soon).