The choices are limited, and even further for those who commute on different bikes.

I have a mountain bike pimped out with a rear rack (and soon to be a front rack), semi-slick tires, fenders, light mounts (I have one headlight and one tail light that I move between bikes), and some other things suited for commuting on it.

I have an old Schwinn World Sport road bike which I recently acquired. I put a rear rack on it, mounts for the lights, and am going to be adding a front rack/basket (undecided) as well as toe clips in the near future. This is my "main" commuter now that I have it.

And all summer I commuted on a Giant Kronos road bike, which was admittedly a poor choice for commuting since the chain stay isn't long enough for the racks I had (heel strike was insane). I love commuting on it though because it is by far the "fastest" bike I have, with the skinny tires and gearing and position just feel right. It's been relegated to recreation and very fair weather rides since I picked up the World Sport.

So the general trend is towards "commuterized" road bikes definitely, but the MTB also serves its purpose with the fenders and general "truck" feel for a bike.