"LoseIt!"
Contrary to popular belief, breastfeeding for three weeks after you give birth doesn't always get your body back to its pre-baby shape. You may actually have to eat less and exercise. Download Lose It! to set a weight loss goal and establish a daily calorie budget. Then keep track of your daily calorie intake and record how much you burn through exercise. For help with your workout routine, try IFitness, a comprehensive database that provides images and step-by-step instructions for over 160 exercises. Follow one of the applications' nine routines for weight loss or strength training and you might just fit into your skinny jeans by summer. (LoseIt! FREE/IFitness $1.99)