Thanks for the help everyone. I'm not sure where they came from, but i did get some corals from Reefermadness about 3 or 4 weeks ago, which has been the only stuff I've added to the tank in a while. I always dip new corals in lugol's, but I guess I will have to start being more vigilant for pests. So far, I've found them only on four corals (none of the new ones, by the way), but they are all over them, so I imagine there must be a lot more of the little buggers in the tank.
Cali-reef, thanks for the heads up on the info.
-Scott