The latest stable release is 2012.05, which can be downloaded here:
buildroot-2012.05.tar.gz or buildroot-2012.05.tar.bz2.
The latest release candidate is 2012.08-rc2, which can be downloaded here:
buildroot-2012.08-rc2.tar.gz or buildroot-2012.08-rc2.tar.bz2.
--> This and earlier releases can always be downloaded 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.