I've been playing with IBM's open-sourced STAF/STAX test automation framework and I'm really impressed. Support is top-notch too via the project's SourceForge mailing lists. I asked 2 questions one day: both were answered in 30 minutes, and both answers solved my problems.
STAF shines when you need to distribute your tests on various platforms, run the tests, get all the results in one place together with the FAIL/PASS count for the test run. I had been trying to do this in the past with a home-grown XML-RPC agent written in Python, but it was not industrial-strength and it had very few reporting features compared to STAF.
You can run a regression/smoke test based on STAF every night, and have STAF send you an email with the test result. Perfect for continuous integration!