Recumbent bike in front of the computer while reading the New York Times.
I also use free weights twice a week while watching the evening news. I highly recommend this form of excercise. For under $50 you can generally buy a set of weights and an excercise book. I also recommend anything written by Joyce Vedral. Her books are geared for the beginner and the older woman. They are very easy to follow.
Eat lunch at my desk while I work, then go to the gym (which is located about a half a block from my office) on my 1 hour lunch break. Between walking time, changing time and showering time, that leaves me about a half hour of actual exercise time. I try to do this 5 days a week, but usually only manage 3 or 4 days a week. Still, it’s probably better for me than napping in my car, which is what I used to do on my lunch break.