I tried a bunch of earbuds until I found these Shure SE-115s, $89 on Amazon
I use the smallest rubber inserts and they seal out wind noise so much better than any earplugs I have tried.
The detachable cable is great when you stop to get gas and want to keep the helmet on.
They are designed to have the cable go over your ear which doesn't work with a helmet, so use the right in the left ear and the left in the right ear.
Use the smallest rubber insert, you will want to seat them in as far as possible.
I give them a little finger/spit lube when I put them in, then put on the helmet, then pull the helmet off to one side, slide your hand up in there and seat them in one at a time really good and as deep as they'll go. Fasten chin strap and you're good to go. You'll know you have them in right when you can't hear anything and you have a head voice.
I use the treble boost setting on my ipod since the eq is a little dark on them. This results in very nice natural non-fatiguing high end. I also use the volume leveling feature on itunes to keep the tracks at the same relative volume.
When removing your helmet, reach in on each side and remove the earbuds first.
I do music for a living and love the way these sound. I'm very careful with my ears and can't stand wind noise.