Robert,
We are using a tool from Compuware named Qaload. I'm not sure I'd fully recommend it though. (I'm not on the testing team that's actually using it, but I've been helping them some on it.) The testing script gets written in C, and the bank of testing machines we have in place don't seem to be able to provide a consistently high load on the system we are testing. But it's entirely possible that it's a configuration problem on our side too so get some other opinions before making a decision.
>Can anybody recommend me a "Web Application Stress Tool"; perhaps with download link?