On the Nike Running website if you use some kind of tracking device like the nike+ ipod app or nike+ bracelet you can start a challenge and run against other people you invite to the challenge and track your and their progress.
I love this idea!
I would LOVE to link up with this! Especially since I am running 3 races (possibly 4) this year!
You know I'm in.. I just don't quite know when yet.. :)
I would do it (even though I haven't ran since DC). Crazy!!