Sage has two build bots.
Release Buildbot
The first builds entire tarballs (e.g. all the alphas) on a wide variety of machines, and can be found at http://build.sagemath.org/sage/ .
Patch Buildbot
The second pulls and applies patches from trac and can be found at http://sage.math.washington.edu:21100/ticket/ or from links on the individual trac tickets. This is still very much a work in progress, but the latest version of the code lives at http://sage.math.washington.edu/home/robertwb/buildbot/bot/ . Eventually this will get moved into Sage where it can be edited using the standard procedures and more widely deployed.