There is a number of stress testing tools available for IIS. WCAT and VSTS/ VSALM are probably the best known tools today:
For an overview of both tools, you may consult these blogs:
Something to be aware of is that FIDDLER logs can be exported to both tools and integrated in a test scenario:
When performing simple tests just requiring to stress a particular URL, the above tool may be overkill and you may be more interested to use a simple GUI stress tool like the one used in the video "Improving Performance with Native Output Caching":
Since I couldn't get hold of the above tool, I decided to write my own URLSTRESS tool. The tool currently looks like this:
I'm also posting the tool's source code in case you would like to use it as a skeleton for your own stress tool.
Happy Web Stressing!