I agree with Scott - my 2003 3.0i motor has the oil filter housing gasket leak. I dropped my pan and cleaned the motor and drove it (do not drive without belly pan!) and no leaks found but after time it is leaking into the bottom of the pan where the oil drain flap is located. What I did was put paper towels inside the flap door to catch the leak.
I have purchased oil filter gasket for $5 bucks. The issue is the time to replace the gasket takes an estimated 10 hours since you have to take out the alternator etc. from my research. Big job so I am going to wait to do the water pump and thermastat at the same time to make the job worth while.