Blue Magic is my favorite. It's a non-abrasive metal polish. You can also use it to take out light to medium scratches on your paint. Believe me, I've made a LOT of tree striping go away with this stuff. I use a random orbital and a terry cloth pad.
You can find it in most auto parts stores and also stores like Target.
http://www.carpunky.net/B0002JM8MC/Blue-Magic-Metal-Pol...Cream-7-oz--jar.html