Put some money on it.

Coming soon a website (StickK) that lets you do it.  Set a goal, if you don’t achieve you pay a set amount (payment to go to charity).  The example they give is weight loss.  Regardless of what the goal is, this is perfect for me.  I’m at my best, most disciplined self when something’s actually on the line.  And my money is a pretty good motivating factor.  In any money based competition (e.g. recently had a bet with some buddies who could lose the most weight in a month, $50/head into the pool, winner takes all… yes I won, I CRUSHED), I get as much satisfaction from keeping my money as I do from getting the winning money.