WebDriver (also known as Selenium 2.0) is a web testing tool that is both useful and easy, which is a very rare find. If you are doing web development with ASP.NET, you need to take 30 minutes of your time and go try out WebDriver. That is all the time it will take to get you hooked.
To launch a browser you need only new up a Driver object for that browser. I used to create a new Driver in my TestFixtureSetup, and then close and dispose of that in the testFixtureTearDown. However now that Firefox does not persist my windows login credentials it can be very frustrating to have to log back in for every test fixture.
A solution to this problem is simply to share a single WebDriver across multiple TestFixtures. Fortunately NUnit's SetUpFixture makes this very easy to do.