Listening to music whilst riding isn't everyone's cup of tea, but here and there I like to get the tunes rocking when out on XC missions- it's good to get into a rhythm.
The only problem I get is listening adjusting the volume and changing tracks whilst riding- there are a few small devices out there, but they don't really work too well with gloves on (etc).
The Belkin Sport Command is weatherproof and allows your iPod to stay out of harms way thanks to the small reveiver that plugs into the bottom of any iPod (except Shuffles).
There are two straps supplied- one for arm use, and the other could be used to strap the device to a bag (etc). Also included is a split ring carabiner for attaching it to clothing (etc).
This simple dongle keeps the wireless thing working when in your pocket or bag...