Bootable USB stick using Mac
Instructions (five steps) to create a bootable usb stick (with iso file):
hdiutil convert -format UDRW -o /path/to/target.img /path/to/ubuntu.iso
diskutil list
diskutil unmountDisk /dev/diskN
sudo dd if=/path/to/target.img of=/dev/rdiskN bs=1m
Progress can be checked using CTRL+T
diskutil eject /dev/diskN