I work out at least twice a week at the gym, and try to do something at home...I count mowing the lawn as exercise, because I push it fast and get a good sweat up.
I use an elliptical trainer or a stationary bike. I also lift on weight machines-they give me a more balanced effort that free weights.
the NMSS has a DVD of yoga and tai chi for MS patients...go on their site. It's gentle and helps stretch those tight muscles.

My neuro also told me to swim...it's the best for MS patients...