I too suffer away daily in a small cubicle in a relatively motionless state all day and am interested in trying the ideas some of you have mentioned. If anyone comes up with any more ideas, please post them. I'll try just about anything I can get away with in my cube, despite how ridiculous it may look. If people don't like the strange fitness show I'm putting on they can look somewhere else.
One suggestion I do have, bucs, is to make drinking as much water as possible a personal daily goal. Water is extremely important to getting (and staying) healthy and you can consume a fairly good amount while sitting at the office. Doing so encourages you to get up more often for frequent trips to the water cooler and equally frequent trips to the bathroom.
Of course I'll still exercise in the mornings and evenings, but I like the idea of finding ways to accomplish SOMETHING useful for my body during the work day.