In January, I got in on a Living Social deal at the local ice rink. 50% off skating lessons (8-week program). So I bought one primarily for my 5 year old, but figured I'd take a shot, too so I can skate with him.
With a grand total of 20 seconds on skates previously, I ventured out on the ice for my first lesson.
I was hooked.
Since then I've been skating a minimum of 1 hour per week, many times 2-3 hours. With the wife on part time for maternity for the time being, I have Wednesday and Friday mornings free, which also happens to be when the Ann Arbor Ice Cube has open skating in the early morning.
So as a bonus to the enjoyment and exercise (I've roughly calculated my own burn at 800 calories/hr), I also get to skip traffic, as there's almost nobody on 23 between 5:30 and 6:30am.
So yeah. No traffic, good cardio, and if you ladies want to tone up calves and hips I can't imagine a much better activity.