The nice people over at 
Penguintosh have created a Linux USB Creator.  Allows you to select a linux distribution (either from a list or browse for a Local ISO file) and then installs it to a USB device (complete with Bootloader).
Only works with OSX Lion (at this stage).
Download 
here & more information available 
here:
 
It don't work for me.
ReplyDeleteOSX Lion on Macbook.
Tried with 2 different USB stick but the USB is not showing when starting the computer holding ALT. Only rEFlT and recovery disk shows up.