My housemate told me about this app you can download onto a smartphone/blackberry/iphone etc. It is really really good, if you run with your phone playing the podcasts you should definitely think about downloading it.
It tracks the distance you run, the speed you run and even the amount of calories you've burned!
I completed w5r3 (the scary 20min run!) and I ran (including the 5 mins running each way) a total of 4.9K, pretty impressive for week 5 I feel!
It's really interesting to know how you are progressing in terms of distance as well as timing!