Just to be clear, though - it's rear suspension that's really, really, really not recommended for commuting (unless you have really pricey rear suspension, but then you'd be unlikely to ride it to work...). Rear suspension is really terrible for you efficiency. Front suspension isn't nearly as bad.

Another thing to do is to put "slicks" on the bike. Knobby tires are slower, a rougher ride, and counter-intuitively, less grippy than slicks when you're on the road. The knobby part works on dirt by digging into the dirt to give you more traction. On pavement, it's solid and it can't dig into it. All that happens is that the space between the knobs is space where the tire has less contact with the road. I like the Panaracer Pasela tires, myself - $30/tire and puncture resistant, they're the cheapest good puncture-resistant tires I know of.