We just migrated from a hand-rolled set of Perl scripts to a Buildbot setup. I found it because that's what Google's using for Chrome.
You can do nightlies, or it can integrate with source control to do an isolated test build whenever anybody does a checkin, or a variety of other things. It's also parallel; you can have more than one machine in the build farm, either for specialized duties or just to handle more load.
The entire system is written in Python, so it's platform-agnostic, which is important if you need to do builds on more than one platform. It can do anything you can do from the command line; we have it calling MSBuild for user-mode components, a DDK build
for kernel-mode pieces, and running products for unit test builds.
Out of the box it supports most OSS source control tools, but if you're using TFS or something else you may need to modify the package that you install on the slave machines.