Free weight isolation exercises is the way to go.
Look for exercises that target your triceps, especially. That's the back muscle on your upper arm. Bicep builders are good, but toning the triceps will pull in that arm jiggle.
To tone, do lots of repetitions at lower weights (instead of the heaviest weight you can handle, go with one that feels easy to start with - a pound or two - but will exhaust your arm over time)(to build muscles you want a few reps of higher weight).
An easy to start with exercise is to stand with your arm down and slightly away from your body, holding a purse (or bag of groceries) with the back of your hand forward (palm curled back). Bend your arm up at the elbow slowly, keeping the upper arm still, raising the bag, until your arm is parallel to the floor.
Remember - triceps (& biceps) exercises, low weights, lots of reps, go slow and focus on the muscle.
at 10:32 PM on Jun. 20, 2011