Which open source CI tool is best suited for your application's environment?
For anyone interested, I wrote a comparative review of four open source continuous integration tools here. I looked at Continuum, CruiseControl, Luntbuild and Hudson. I also looked at Anthill, but it's current version seems pretty limited (the commercial version looks OK).
We've been using Continuum for a while: it's a nice, easy-to-use product, but it does have its limitations (no dependencies between projects...). Hudson is relatively recent, with a fairly narrow focus, but looks quite a slick product. Luntbuild is feature-rich and flexible, though I tend to be a little wary of products with commercial "cousins". CC is solid and reliable, but more lower-level than the other tools.