This thread inspired me to time myself in a 5k around the Rose Bowl last week. I keep in pretty good shape with some longer runs, some interval work, running up mountains, and some weights. I've been too busy lately to train often or even play tennis much, so when I work out I try to aim for short intense workouts.
Anyway, I pushed myself pretty hard and got a 20:45 which I was pretty happy with! It's only about 2 minutes off my times from high school when I was training much more consistently.