I am a recent fan of chair exercises. I have some problems with knee, hip and lower back pain (arthritis, glycosylation of tendons) and I find that doing chair exercises is a good way to work some heart-pumping exercise in-between my walks.
I turn on some up-beat music, sit on a stable, arm-less chair (e.g. a kitchen or dining room chair with no arms) and exercise along with the music. I do arm lifts above my head, arm lifts to the side, bicep curls, triceps lifts (hold arm strait overhead with elbow facing slightly forward, make loose fist, drop lower are behind your back and then lift it, drop it and lift it, keeping your upper arm straight up by your ear the entire time), etc. Little arm circles one way and the other (with arms held out to the side) are good for working the shoulder muscles. I also do air punches, blocks and chops (years ago I studied martial arts and these moves are now just part of my dance repertoire -- scary, huh?)
Most 'pop' songs on my iPod last between 3:45 and 4:00 minutes long. I try to do chair exercises to at least ten songs per day, scattered between all my other walking, dancing, stretching, etc. It's a great, fun, easy, quick way to get my heart rate up and increase my respiration for a bit -- very helpful when you have a sedentary job. I even like to do these sitting on the side of the bed first thing in the morning. I'll put in my ear-buds, turn on a medium-rate song and do these a bit slower as a way to wake up and get my circulation going before I stretch up, stand up and face the day.