UNetbootin

UNetbootin allows you to create bootable Live USB drives for Ubuntu, Fedora, and other Linux distributions without burning a CD. It runs on Windows, Linux, and Mac OS X.
http://unetbootin.sourceforge.net/

Rufus

Create USB installation media from bootable ISOs (Windows, Linux, EFI, etc.) It is only availalbe for Windows.
http://rufus.akeo.ie/