I injected some funds into this cycling habit this week, but man is this fun. I am now wired for sound. This is a Firehouse Technology I-tube 2.0 Actually not that expensive at $40. I ride mainly paved country roads and keep the volume low for safety, but this little speaker will rock if you want it to. It's made primarily for motorcycles, but works great on the bike too.

Looks like a nice little speaker. Unfortunately for me, I ride mostly aerobars and putting the speaker on the handlebar would put it right in my face. I have been using some speakers that were made by a local guy that uses magnets to hold them under your jersey. Those work great and allow you to hear the music and everything else around you, including other riders talking to you.