Many moons ago I wrote about Etymotic's fancy noise-isolating earphones, which were a pretty good deal at $69.99. Still too rich for your blood? Here's your chance to try something similar for one-tenth the price. HandHeldItems has the iSolate Hi-Fi Earphones on sale for $6.99 (plus a very reasonable $2.85 for shipping). You also get a free Fishbone cord-wrap gizmo.
Because the tips nestle into your ear canal, the iSolate earphones block out a fair bit of ambient noise--meaning you don't have to crank the volume as much when riding a bus, plane, train, etc. They're like earplugs: You have to push them in far enough to create a seal in the canal. It's a little weird at first, but I find them much more comfortable over the long haul and capable of producing much better sound.
The iSolates have a metal housing and come with a spare set of earbuds. They're available in other colors for a few bucks more, but the $6.99 deal is for the black ones only. I haven't tried this particular pair myself, but four reviewers on the site gave it an average of four stars. If you're still using the earbuds that came bundled with your MP3 player, I highly recommend trying some in-ear alternatives--and you're not likely to find a better deal than these.