The latest stable release is 2009.05, which can be downloaded here:
buildroot-2009.05.tar.gz or buildroot-2009.05.tar.bz2.
The latest release candidate is 2009.08-rc3, which can be downloaded here:
buildroot-2009.08-rc3.tar.gz or buildroot-2009.08-rc3.tar.bz2.
This and earlier releases can always be dowloaded from http://buildroot.net/downloads/.
You can also obtain Daily Snapshots of the latest Buildroot source tree if you want to to follow development, but cannot or do not wish to use Git.