More info at:
Here is a video I made demonstrating the procedure.
Download your distro of choice, in my case Ubuntu Gnome edition
Once that is done, use the command that follows to convert the iso to img:
hdiutil convert -format UDRW ~/path/to/target.iso -o ~/path/to/ubuntu.img
Note: OS X tends to put the .dmg ending on the output file automatically, delete the ".dmg" ending.
Run diskutil list to get the current list of devices
Insert your flash media
Run diskutil list again and determine the device node assigned to your flash media
diskutil unmountDisk /dev/diskN
(replace N with the disk number from the last command; in the previous example, Nwould be 2)
Execute the following command while replacing /path/to/downloaded.img with the path where the image file is located; for example, ./ubuntu.img or ./ubuntu.dmg).
sudo dd if=/path/to/downloaded.img of=/dev/rdiskN bs=1m
Using /dev/rdisk instead of /dev/disk may be faster.
Run diskutil eject /dev/diskN and remove your flash media when the command completes
Restart your Mac and press Alt while the Mac is restarting to choose the USB-Stick or restart your PC and choose the USb from BIOS.
This USB should work for any computer.
(If you see the error dd: Invalid number '1m', you are using GNU dd. Use the same command but replace bs=1m with bs=1M.
If you see the error dd:/devdiskN: Resource busy, make sure the disk is not in use. Start the Disk Utility.app and unmount (don't eject) the drive. )
Thanks for watching