ref4 runs FreeBSD/i386-STABLE
ref5 runs FreeBSD/i386-CURRENT
beast runs FreeBSD/alpha-CURRENT
panther runs FreeBSD/sparc64-CURRENT
sledge runs FreeBSD/amd64-CURRENT

At the moment:

ref4 tests gcc-mainline
beast tests gcc-mainline
sledge tests gcc-mainline

See <machine-name>/STATUS for long-term history.
See <machine-name>/<dated-directory>/... for log files from build/check cycle.