Tricep dips are great for the...drumroll please...triceps--or those muscles on the backs of your arms that my grandmother calls 'boing' for reasons I don't need to explain.  This exercise is nice because it also involves other muscle groups--the shoulders, abs and back all work to keep you stable--your legs too!  Do it right:  Begin sitting on a step or chair with hands next to thighs.  Balance on your arms, moving backside in front of the step with legs straight (harder) or bent (easier).  Bend the elbows and lower body a few inches, keeping the shoulders away from your ears and the elbows parallel to one another, going no lower than 90 degrees.  Push back up to starting position.   Repeat for 2-3 sets of 8-12 repetitions.  If you have any wrist or shoulder problems, skip this exercise.