I have a couple of homemade Walkman/iPod holders that I made many years ago and they work great. However, I just found this gadget holder and ordered it out of curiosity. Very well made and thoughtfully designed. Requires no tools to mount to handlebars. Can be found at Thinkgeek.com
Note: On the website opening pic it doesn't show the 2 fold out arms which support your gadget from the bottom (in conjuction with the 2 side squeeze pads), the pic shows the gadget holder with the 2 bottom support arms folded in/closed. If you click on the "customer action shots" it shows a pic with the bottom support arms folded out.

http://www.thinkgeek.com/gadgets/tra...adget%20holder

Think Geek also has an aluminum tube speaker which comes with a handlebar mount for your bike. This could be a good solution for those wishing to hear music without wearing headphones, (I did not order this one yet):

http://www.thinkgeek.com/electronics...tube%20speaker

And no, I do not work for or have any affiliation with Thingeek or their suppliers...

Attached are a couple of pics of my homemade version gadget holder: