— flash usb stick w/bootable iso

1. diskutil list
   Determines the device node assigned to your flash media (e.g. /dev/disk2)

2. diskutil unmountDisk /dev/disk#
   Replace # with the disk number from the last command; in the previous example, # is 2)

3. sudo dd if=/path/to/example.iso of=/dev/diskN bs=1m
   Replace /path/to/example.iso with the path to the iso; for example: ./windows7.iso. After typing in your sudo password, the process will start invisibly.

4. diskutil eject /dev/disk#
   Remove your flash media device when the command completes. Done!

Referenced from BurningIsoHowto

Bonus tip! You want to see how far the dd copy is coming along? Run in another terminal instance:
$ sudo killall -INFO dd
The process info will display in the original terminal.