What do you mean by stuck? Is it simply on too tight, or was it somehow attached (glue, etc)?
If it was attached, I suggest taking a thin, sharp knife and running it between the skin and iPod all over to break any bonds, and then try to peel it off.
If it is simply too tight, and you cannot peel it off at all, you may have to cut it off, just slice it along the sides of the iPod and take it off in two pieces.