i use these: http://www.amazon.com/Monster-Turbine-Performance-In-Ear-Speakers/dp/B001LNO722

Westone's are the best! great for inside your helmet. 

http://www.earphonesolutions.com/

check out this site for every kind of killer earphone..

Don't all of these just fall out of your ear as you put your helmet on ?

I don't recommend earphones while riding...
It is very nice and cool but..
Couple weeks ago I was riding with 2 friends, listening some flamenco. We came to stop at some mall my friend met someone there I was sitting and listening music when noticed that friends stopped their engines and started to walk of the bikes. I stopped engine too and started to come off the bike and bike tipped on the side, damaging gear shift pedal. Fuu I forgot sidestand. Nice music can suck a lot of your attention and awareness.

I dont think that was the headphones fault. Im pretty sure with or without headphones youd probably never do that again.