UPDATE: Guide has now been updated for flashing straight to Jelly Bean here:
http://wp.me/pPq0u-3x
This is my first post on here. I've been browsing a while and seen this question come up on many different forums so I decided to make a write up for a how to for users on Mac OS X that don't have access to a PC. I've posted it to my blog for everyone. I look forward to contributing more. If you have any questions, please feel free to ask.
Guide: Update your Galaxy Nexus from ‘yakjuux’ to ‘yakju’ 4.0.4 – Mac OS X « Digital Igloo
Thanks for looking!