I, too, have a job in cube land, stuck in front of the computer and attached to a head set. *sigh* Somethings I do to get active are: 20 minute walk at lunch, walk laps on my breaks, walk as fast as possible to the bathroom. I also try and hit the stairs a time or two while walking laps.
SP also has some ideas. Here's a link to one I found: www.sparkpeople.com/resource/fitness_artic