I've talked many times about the virtues of Continuous Integration. To get such an environment working you need a continuous integration server, and a source code control system. To make a project run smoothly you could also do with an issue tracker for bug tracking and the like, and a wiki to help capture all sorts of project knowledge.
Getting a good environment with all of these things up and integrated together is a tougher job than you might think. Inevitably we found we would be messing around for a week or so on new projects to get the build server set up with all this stuff. I mentioned before that our London office has grown a really sharp deployment team, one of their side jobs has been to sort out putting together a build server.
It's been trialled on a few ThoughtWorks projects, and now it's available for everyone. Buildix is a complete development server, tested in the field by ThoughtWorkers (a very demanding lot), and available for free.
It's free because it's a collection of open-source software that our deployment wizards (Chris Read, Julian Simpson, and Tom Sulston) have integrated together with some of that magic powder they found in the fridge.
The server uses Knoppix (a Debian Linux distro) as its operating system. It's a live CD so will run just off the CD drive if you want to play with it. As with any of these live CDs you can then install it to your hard drive easily and you have the full server ready to go. There's also a VMWare Image.