I have a couple of homemade Walkman/iPod holders that 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: In the picture 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...0ipod%20holder

Here is a pic of my homemade version: