A clicking is more likely to be a front u-joint (an axle shaft u-joint in particular).
You'll get a bad vibration under acceleration with a rear driveshaft u-joint, so I agree that this is the likely culprit. Put the parking brake on and the transmission or t-case in neutral (with the engine off so you don't accidentally drive over yourself) and crawl under there. Grab the driveshaft near the u-joint and try to rotate it and wiggle it back and forth. If there's any play AT ALL, then the u-joint is bad.
Replacing a u-joint is a good learning experience. Go to your local parts store and buy a new u-joint. If you're careful and don't bend the ears, you can replace it with just a hammer, a socket, and a pair of pliers. It's easier to do it with a good vice or a press. Search for a thread with instructions.
Assuming that your screen name reflects your ZJ, when you hit up your local parts store, make sure to specify that you've got a 'Niner. The 5.9L came with a larger rear u-joint than the 5.2L.