Actually from the look of it (the old figer the fluid test!) it's oil, not quite as bad as it looks, never cleaned it off after I fixed my valve cover lead, but I'm pretty sure that my rear main is leaking, been to lazy to throw the dye in the engine to trace it out...
If it is the rear main, well, that'll be the kick in the ass to drop the trans. and replace my flywheel, got a few chewed up teeth from a bad Autozone starter I put in a couple years ago (the week it was in the car was long enough to do the damage...was too busy to pull it right out).
Ahh..Jeeps...never ending project!