Some wet sanding with some light sand paper followed by some polish and polisher if you have one, should bring them up a treat.
I've also seen some people spray black around the outlines of the tail lights after doing this and it really makes them stand out even more.
I think Frank on here might have done this?
yes i have. very easy step to do. pretty much what Infamous has say. i use 1000 grid sandpaper first. then move to 2000 wet sand. then, use plastic polish. after you polish it. spray a light coat of clear over it. and BAM!!! you got yourself some new looking tail light.
for extra work on your tail light. you can bring it out with painting the border black then clear coat it. look alot better.
cheer and hope you get it back to new mate