Try making your test execution multithreaded

I use to run GUI-level automated test suites with thousands of tests in them. I've run web service tests with tens of thousands of tests. Early on, I was using tools like IBM Rational Robot. In traditional vendor tools (like Robot) test suites like this were painful because you could only run one test at a time per machine. That means if you wanted to run your suite faster, you'd either have to add more machines, or make your existing machines faster.

Bah on that...

One of the reasons I was so quick to switch to Watir when it came out was that it allowed me to run multiple tests at the same time. Because I could run multithreaded (and because the tool leverages the DOM instead of the Windows API), I could run in a fraction of the time (a fifth or a tenth). And all that with no additional resources.

Depending on what you're testing, this may or may not be an option. But if you're doing automation at all, my tip for the day is to look at multithreaded execution.
AutomationMichael Kelly