Are you sure it's engine oil and not tranny fluid. Just asking --- because you sure don't want to blow out your transmission.
Whenever I have had a leak like yours, that was not immediately traceable, I get a couple cans of engine brite cleaner, my car ramps, rags, and head to the local self-car wash place. Clean everything you can from the bottom (Don't use that stuff on the top of your engine!!!). Wipe down any remaining fluid residue. Usually I can pinpoint the leaks when I get home. Then it's a matter of deciding if the problem is a DIY project, or not.
Be sure to check the transmission pan. Service kits (gasket, filter, washers) are only ~$25 at this site, and could save your car.