This site has reviews of a wide range of headphones & earbuds. I'm looking for some new, comfortable earbuds that have good outside noise decibel reduction. If they come with a case too, that's cool; otherwise I just wrap them around the iPod...
Among the best brands are
Shure, Bose and
Etymotic. I've also been happy with some
Sony's in the past.

UPDATE: I got some very sweet Etymotic research earbuds for christmas! and then less than a month later, I lost them!?!???!! I've NEVER lost a pair of headphones before in my life, so of course I'd start with some $100+ ones :(