Apart from a quick shopping adventure I can't think of any MUST SEES in Dubai. As you know the airport is in a great location very near downtown and customs is quick both getting in and out. The longest part is the walk from the gate to the outside and back in so no need to allow a ton of time as you would at say NRT.

Wafi city is close but it is just a shopping complex with a good variety of shops and fairly interesting people watching. You can walk around the creek and grab some food on or near the river but that is not a long process. Some have suggested going to see the Burj Al Arab hotel, and that is certainly an impressive site and worth a visit. Just be careful about the distance as cabs, although fairly cheap, can start to get expensive if they are shuttling you around town to points as far as the Burj.

Lastly I do remember seeing Emirates/Dubai booths set up at the airport and around the customs hall with information about short stays in Dubai city. I am sure you can pick up some information and gather some knowledge there as to what you would want to do. It is not the most interesting place on earth to layover but it is far from the worst.