Some time back Bill Barnett wrote a great blog post on how you could go about creating a custom load test plugin for your Team System Load Tests. The post provided two things, it showed users how easy it was to create a custom load test plugin for VSTS and two, it provided the user with a great sample that they could start using right away.
I decided to take his advise and add a user interface to the plug-in so that users could truly “Dail-A-Load”. I presented this topic at a IndyTFS SIG meeting and it was a big hit. If you are interested in checking out the tool you can download it from the IndyTFS website. .http://www.indytfs.org/sig/Downloads/tabid/55/Default.aspx and download the July 2007 Testers material. I have some Web Request, Web Test, and Load Test plugins, plus the slide deck.
I have not tested this with VSTS 2008 yet, but it should still work.