I suspected I have a bad timing chain cover seal causing a minor oil leak. But when I removed the harmonic balancer pulley, I noticed quite a bit of oil on the back of the pulley and where the crank shaft meets the balancer.  The balancer was replaced by the previous owner.  Are you supposed to put a dab of RTV on the woodruff key?  I suspect this didn't happen when it was replaced last.  I'm going to replace the seal anyway.

i've redone the balancer seal/timing cover/oil pan gasket 3 times on my car  because i've had the same leak .   mine is coming out of the balancer seal.  the thing still leaks and i'm done with it!
 my suspicion is that the end of my crank might be just slightly bent causing it not to seal up.
i'm putting up with it until i can swap out the motor.  hopefully it won't be too many more years.

i hope you have better luck than i did.

You can use some sealant on the inside of the balancer hub, but it is really rare that they leak there. If that's where the leak is, the oil would be on the front side of the balancer, not the rear.
Timing cover seals leak more often than not. They're thin to start with, and any distortion while installing them will create a leak point.
Another area that has been known to leak is where the timing tab is welded on to the cover. The spot welds can break loose a bit over the years, and oil will leak from there.
If you go into this and replace the seal, get a good one from NAPA, or the dealer. You'll have the best luck if you start with the best seal. Then press it in, don't hammer it. If you have a chrome timing cover, it helps to use a small amount of Permatex Aviation Sealer around the outside of the seal before installing it. This will work on regular steel covers, too, but the chrome ones seem to leak more often.

Also, as Jeff mentions, if the snout of the crank is bent, ain't NO seal gonna stop the bleeding there...

I stopped a harmonic balancer leak with one of these.  Recently I used one on a front wheel drive axle shaft to quit a leak.  In both cases the shaft rotation worn the area the seal rubs. johnu2007-07-18 18:56:09

I  agree my shaft seal is worn and probably was not replaced when the balancer was last year.  Here's a pic of what I'm talking about.  See the oil inside.  I haven't removed the balancer yet cause I'm replacing my valve stem seals.  For a 1st. timer, so far so good. .  Thanks for all the feedback!