Plyometric box jumps.
Just about any interesting bodyweight exercise you can think of that utilizes the things around you.
A jog combined with several intense sets of bodyweight exercises like the ones listed above is possibly the single most effective fat loss workout you can do. I call them "Run and Gun" workouts. You should give them a try if you want to burn fat and lose weight fast, in a way that will explode your metabolism and add lean, toned, sexy muscle to your body quickly! Just make sure you're always moving and keep rest to minimum. Absolutely no sitting or standing around!
Check out this great video of a fantastic run and gun workout example routine being done in the city of Philadelphia:
p.s. Thanks to Mark's Daily Apple (a fantastic "primal" fitness blog you should check out!)