Do you have those friends who make you loathe yourself because they post on Facebook about how long their morning jog was? They're probably using MapMyRun. At 25 million downloads, it's one of the most popular fitness apps on the market. With a robust online social community, it connects with other devices to store your fitness data, including how far you ran, where you ran, and your heart rate. Information on how much your self-esteem has fallen the two weeks after New Year's, however, is not given. (Available now, free).