If you don't own an iPod nano but still would like to track your mileage in an affordable way (the other option would be a Garmin GPS which is $$$), the Nike Plus Sport Band is a great alternative. It's very lightweight, it easily plugs into any computer via USB, and you're connected to the Nike+ running community!

Be advised that you will need a Nike+ shoe, or you'll need some third party sensor holder that will attach to any of your existing running shoes.

Track your walking and running progress with the flick of your wrist. No longer tied to your iPod, your stats are legibly displayed on the band whenever you are wearing Nike Plus enabled footwear. Simple. Cool. Nike.

And, just to get you motivated, here's an update on the 2008 Boston Marathon: Robert Cheruiyot finished in 2 hours, 7 minutes and 47 seconds. The women's top finisher, Dire Tune, beat out the 2nd place finisher, Alevtina Biktimirova by a mere 2 seconds. Beat that.