Here you go. Instructions for building a bootable flash device for Mac OS X. The article is about SD cards and newer Macs, but the coments point to USB as an alternative for older Intel-based Macs.
For the hardcore users out there, Apple decided to give the SD port super powers — you can use it to build a bootable SD card. That bootable card can then become an awesome tool for performing emergency hard drive repairs, data recovery, recovering deleted files, and much more