Best load and stress testing tools

A while ago I answered the following question on SearchSoftwareQuality.com’s Ask The Software Quality Expert: Questions & Answers.

Can you please tell me which tools are suitable for load and stress testing?

Here is a clip from my answer:

I've found all of those tools to be good solutions, depending on what I was testing. Along with each of those tools, I often use a host of monitoring tools, anything from the simple like Perfmon to the complex like CA Wily Introscope . If I had to choose one for Web services testing, I'd probably choose soapUI. If I had to choose one for websites, I like IBM Rational Performance Tester. For everything else under the sun, HP Mercury LoadRunner probably has a plug-in that supports it. In general I prefer open source to commercial, but if the commercial solution is a better solution for my problem, I'll pay up.

You can find the full posting here.