What motivates you to move?

My Nike+ Mini dances around the screen
giving me encouragement

I am generally externally motivated.  I know, I know, we talk to parents all the time about helping kids develop internal motivation but the truth is, when it comes to doing the things that are good for me, I look for motivation from many sources.
My motivation for running has been boosted by my participation in some online running challenges.  I started with the 100 Mile Challenge blog (currently on a break).  Then Lori created a Spring challenge on her fitness blog. Last December, found the Nike site.  I can sync my runs using my phone and my Nike+ app but even better, I came across a monthly running challenge - Women Run 50 miles. 
So, here is it, November 5, I  have run 7 miles since November 1 and I am in 15th place!  But, today is Saturday and I know I can get in a nice run so I am expecting to climb up that challenge listing and who knows, by the end of the weekend I might be in the top 10! 
What motivates you to move?