1. Join a Gym. Now that you have some extra money, go join a gym. Working out at a gym has advantages over working out elsewhere. The environment helps motivate you and keeps distractions that can pop up at home to a minimum. The equipment and staff can also help you reach your goals a lot easier than going it alone.
2. Exercise Equipment. If you don't want to join a gym but still want machines, you can buy some home exercise equipment at your local sports store. You can get bars, free weights, resistance bands, benches and if you really want to spend some money, you can buy professional equipment. If you have a lot of extra space in a garage or empty room, you can start building your own home gym.
3. Bicycle. Buying a good road or mountain bike will help you exercise and have a good time. Bike riding is an excellent form of cardio and if used right, can even save you some gas money. Use a bike to buy a few light items from the store, go to the gym and run errands. Using a bike to save on gas can also save you time since you won't have to do cardio later.
4. Personal Trainer. If you join a gym but have no idea what to do there, you can use your stimulus check to hire a personal trainer. A trainer can set you up with a routine and motivate you to get into shape. Trainers can be quite expensive so hire one only after you've tried exercising by yourself, with a friend or taken a group exercise class at your gym.
5. MP3 Player. Buying an MP3 player will help you exercise. Listening to music you enjoy will help you run, bike or walk farther and faster and motivate you to work harder in the gym by lifting more weight and getting a better workout.
Also find ways to improve your diet with your stimulus check.