pushups! there are so many variations - on your knees, at an incline (hands on coffee table, chair, anything), on an exercise ball (one of the big squishy ones, hands OR feet on ball) against a wall REALLY slowly, holding for several seconds at the bottom.... i could go on. then you can also focus on a sepcific muscle by the position of your arms and hands - really wide, close together, keeping elbows at your side.

make sure you use proper form. your head should be relaxed and looking straight ahead - not at your belly button. shoulder blades down and back, this will help keep your traps (muscles up near the neck) relaxed. hips tucked, belly button pulled in and up (like there is a string from it out through your back that someone is pulling on)

I know I'm late, but I love putting my back and neck on an exercise ball and taking my dumbells and doing the exercise I have no idea of the name of.

You put your arms straight above you and the slowly lower with arms barely bent out til they are like a T out from your body...do you know what I'm saying? www.fitnessmagazine.com has some awesome exercises to be done at home, I was doing some of them while I watched Alias yesterday on the ball. You make sure your upper body from your shoulders to your knees makes a straight line, don't let your butt hang down on the ball and it will work your core at the same time. I think the exercise is called like butterfly something...maybe. Sorry I can't remember, but as you bring your arms back up to above you, you are sqeezing your check muscles. Feels good.