You'll get better traction asking this question in the Commuting forum as I am sure there are plenty of commuters that use mountain bikes.
That being said, maybe you can look at using Ergon grips or any of the knock-offs. I made fun of Mtnbiker66 because he uses them but later decided to put them on my family/city/commuter bike (Surly Big Dummy) and think they are pretty good.