humm 2day I went out and started my jeep (I start it everyday and let it warm up, to make sure the oil circulates thru the engine, so that the seals don't get dried out from sitting for so long), b.c I cannot drive it at the time cuz my registration got suspended. anyways, I let it run for like 10 minutes, then turn the AC on and I heard a CLUNK from inderneath the jeep, it came from under the Front seats. does anyone know what this may have been, this is the 1st time I have heard, I will check 2morow and c if it does it again.

Could have been your exhaust vibrating when you turned on the AC.

I heard something like that last week. It turned out to be that my jack had come loose from under the rear seat. It kinda freaked me out at the time, though, since I was driving down the highway.
Check your tranny mount, too, and u-joints.