I've always been extremely pleased with my Monoprice headphones.
If you can get a good seal (might need some new rubber pieces), these are FANTASTIC. http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10823&cs_id=1082303&p_id=8320&seq=1&format=2
They're bulky though, so they don't fit inside a motorcycle helmet or anything.
These ones are much cheaper, and obviously don't sound quite as good. They still have decent sound, but they're slightly overly-bassy, and with a slightly muted mid-range. Definitely still worth $5 though, and they do fit inside a motorcycle helmet. Plus, you don't have to worry about thrashing them around. http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10823&cs_id=1082303&p_id=8321&seq=1&format=2
That's my $0.02, anyway. I've compared them to every pair of earbuds I can get my hands on (even ones up to $90), and the 8320's (the ones I listed first) always at least hold their own.