Sitting exercises?
Answers: You can do Kegel exercises all daylight and no one would ever thought.
not exactly discreet
http://www.sparkpeople.com/resource/fitn...
Here's one I can think of.
Sit straight, centered. Back supported. If you can, put your hand just above your knees, press down considerately, and lift your heels. This will work your calves.
You can other tense your muscles...such as your abdominals (tummy), glutes (butt), arms, legs, etc., for a 10-second count. Relax, next repeat.
However, none of this is aerobic exercise. If you want to lose 5 or 10 pounds, aerobic exercise is the best way. Jog, do a step-aerobics class, ride a bike, skip rope, etc. Anything that get your heart rate up and keeps it up for 20-30 minute a time. This is not hard, and you can do some of it within the privacy of your room.
Good luck!