Quick resistance: How about a couple of quick sets of forward lunges or squats to help define your lower body? These exercises take very little room to perform and can even be done at your desk. A couple of sets of pushups will go a long way in toning your upper body as well. You can also tote along some exercise tubing in your purse to do a full-body strength-training routine before you grab a quick sandwich.

Amp it up: When you have limited time, work out at a higher intensity. You'll get a higher calorie-burn bang for your buck. For example, if you weigh 135 pounds and you typically walk on the treadmill at 3.5 miles per hour for 30 minutes, you'll burn about 120 calories. But raise your speed to 4.0 miles per hour and add a 3 percent grade and you'll boost your calorie burn to 185 calories.

Higher-intensity weights: The same principle applies here. Moving through your weights faster with less rest between sets will not only help you finish up your workout in a shorter period of time, it will also burn more calories. If whipping through a weight workout is not your style, opt for heavier weights and fewer reps, a real time-saver that can also help build more muscle. For instance if you normally do 15 reps of a bicep curl with 10 pounds, try 12 or 15 pounds for 8-10 reps.