Where are most common oil leaks?

I got a nice oil leak I gotta fix, and I am having trouble tracking it down. I got a leak in the power steering pump too, but that is just another project, so it is making it hard to track where the oil comes from. I was wondering if there were any common places that it comes from. I can see that it looks like it is coming from under the valve cover, but I already changed the gasket and it is bolted down tight, and it doesn't look to be that much, plus it is only on the passenger side that it is leaking. Anyone know of any other common places other than the rear main? I really don't want to change the rear main, but if that is what I have to do, it is what I gotta do. The reason I didn't suspect this first is because there is oil farther foreward in the engine. Anyhow, thanks for any help you can give! Christian

rear main seal
o-rings there the oil filter mount connects to the block

these are the 2 most common places

Pan gasket could be leaking in front,along w/the rearmain seal.If your gonna swap out pan gasket,might as well do the RMS and check the oil pump while your there.Do a search for rearmain seal,there are several excellant write ups,some even have pics and step by step inst.

i've seen a couple of XJ's (mine included) that had their valve cover gaskets leaking toward the rear, which then runs down the back of the block so it looks like it's coming from the rear main.