Do a search on cardio...we just finished a good thread not too long ago, but for a quick opinion here is mine.

Cardio after a workout is not the most beneficial because your body's cortisol (stress hormone) production is at it's highest.

That is why it's so important to consume your carbs, and creatine within 30 minutes following a workout. Follow that about 60 minutes later with your protein. If you're doing cardio post workout then you're staying catabolic. I still believe that cardio first thing in the am on an empty stomach with just some caffine or a thermogenic is the best way to go. You'll burn more fat and you're gonna speed up your metabolism first thing.