Lumosity is a free app that will help "improve your memory, attention, and overall brain performance through scientific brain workouts.  Lumosity creates a Personalized Training Program that helps you achieve your goals: (App Store). Currently on the Best New Apps list for education and has plenty of admirers.  The Harvard Business Review said, "Designed by neuroscientists, a brain training approach such as Lumosity builds on breakthrough concepts such as neuroplasticity and fluid intelligence."