Source for the latest release can always be downloaded from http://www.busybox.net/downloads/.
Each 1.x branch has bug fix releases after initial 1.x.0 release. Also there are patches on top of latest bug fix release.
Latest releases and patch directories for each branch:
1.10.1,
patches,
1.9.2,
patches,
1.8.3,
patches,
1.7.5,
patches,
1.6.2,
patches,
1.5.2,
patches,
1.4.2,
patches,
1.3.2,
patches.
You can also obtain Daily Snapshots of the latest development source tree for those wishing to follow BusyBox development, but cannot or do not wish to use Subversion (svn).