Mike,
I was worried about transmission problems (ie final drive) or CV/axle
problems, but someone mentioned wheel bearing problems.  I was able to
replicate the noise after jacking up the car and putting it into gear,
and it appeared to be coming from the right front.  So then I take it
to a shop and they inform me it's the left front wheel bearing.  Fine,
something about traveling noise and easy to get the side wrong,
whatever.  But when they told me it would be $400 to replace a $100 hub
and wheel bearing assembly (that only takes 1 hour and 4 bolts of labor
to replace), I started getting suspicious.  And when I went to pick it
up last night, they hadn't replaced it because they said my rotors were
so old they would be too difficult to remove without damaging.  They
would have to replace both rotors since you shouldn't replace just one,
and I had the more expensive vented rotors.  Can you believe this?  A
mechanic can't remove rotors from a 3 year old car because of excessive
rust??  What a load!!  Instead of laughing at him, I got my car back,
ordered a new hub/bearing assembly for $85 (instead of the $250 parts
charge the mechanic wanted), and plan to do the job myself this
afternoon.  I expect to save over $500 by doing it myself.  We'll just
see if a little penetrating oil can't loosen up those rotors.