I've been annoyed lately with the pushup. Every aerobics class I go to the instructor demands pushup after pushup. In the weight-lifting room everyone's slugging through chest presses and more pushups. Now don't get me wrong. I love pushups. They're a fabulous and challenging exercise. What annoys me is the overuse of the chest muscles. All day long women hold babies, type on the computer, do dishes, clean the toilet (yuck) and we lean forward - stretching the back muscles, rounding the shoulders, and strengthening the chest (the purpose of the pushup). If we don't balance with some effective strengthening of the back we're going to have horrific posture.
So by all means do your pushups. They're great. But don't forget to strengthen your back with seated rows, bent-over rows, and reverse flys and to stretch your chest (my favorite is to place both hands on an open doorframe and push my chest through the door). Strengthen your back, improve your posture, and you'll look and feel great.