Apple has released a new utility called the “Lion Recovery Disk Assistant” which will allow users to make a recovery partition on external drives, which includes USB.
The catch is you must have the Recovery HD already installed on the Mac you’re creating the disk from.
Apple’s instructions are simple:
To create an external Lion Recovery, download the Lion Recovery Disk Assistant application. Insert an external drive, launch the Lion Recovery Disk Assistant, select the drive where you would like to install, and follow the on screen instructions.
Check out the support document and download the utility below.
(via Apple Headlines, Apple Support)