I've been running a zombie apocalypse based RP group since August of 2007. It is (was, until the shutdown of MSN Groups) a good and active group, with lots of members. Currently, there are only three or four of us (since most people seem to have died suddenly), but I intend to see it come to life once more, like the zombies I so love killing.
If you're interested in joining in on the zombie slaughter, click on the bigass image/link above. If not, I hope you get eaten by zombies. (Just kidding. But not really.)
At Apocalyptic Echoes, we're less of an online forum and more of a family. A family that exists on an online forum and writes stories about the mass slaughter of zombies. Warms my heart...