Put a dollar in a jar when you finish a work out. When you hit a goal amount treat yourself to a reward. (massage, new pair of jeans, etc.) Another awesome way to get motivated and get a reward at the same time!
Workout tip jar. After each workout, tip yourself a buck. After 100 workouts, treat yourself to new shoes or clothes or massage. But only a buck? Thats a 100 workouts at a week so in a year i get a treat!