I was in the parts store last week for one of the many other vehics I have to maintain and saw this $12 Turtle wax kit for fixing yellowed headlights. I figured I'd give it a shot because my healights were more yellow then my turn signals.
It's a little box with three sanding pads, a spray bottle of "lubricant" and a bottle of polish/wax. It seems to work like polishing fiber optics. Start with the roughest sanding pad, keeping the surface wet the whole time. Work down to the finest pad then wipe clean and use the polish.
It ACTUALLY worked!!!!! Total time about 1/2 for both lights. I even touched up the fog light lenses while I was at it.
Best money I've spent in a while. It was a little rough on my back and arm, leaning over and doing the whole Karate Kid thing, Sand the fence, wax on wax off. I think I'm going to bring out a stool so I can sit down and do the whole process a second time to see if I can take out the rest of the roughness/yellowing that I missed.

 

Let us know how they look in a few months. It seems like others have tried polishing their yellow headlights only to have them yellow again in a few months. If this product keeps them from yellowing for the long run I am definitely interested.

 

also you can take a mag/wheel polish like "mothers" or a buffing compound to the lenses. just apply the compound like you normally would with hands or buffer. if that makes a difference be happy with it or go buy a kit like mentioned above from an auto parts store for even better result.

 

I used a different brand, not turtle wax that had thee same sanding process followed by putting a clear "sealer" on the headlights. Big Improvement! Six months later, they were yellowed out as bad as before, so I did what I should have done in the first place--replaced them.

I hope you have better luck than me.

 

Crystal View for 20 bucks at Wal-Mart worked great on mine. I don't think you can beat it. See it at MyHeadlight.com