I haven't ridden very much in the past month. But I've been walking and jogging quite a bit, all as part of my commute.

Linking up with public transit, I can count on getting in 4 or 5 miles of walking/jogging throughout the day. The good part about that is that when on foot, I can appreciate my surroundings more and let my mind wander a bit. On the bike, it's great, but I really have to focus more on what I'm doing, the road and the traffic.

But I've noticed that for the most part, cycling wins hands down (in my case) as far as cardiovascular workouts go.