GParted (Gnome Partition Editor) is free tool for managing disk partitions. It can create, delete, copy, move and resize partitions. It supports many different filesystem types such as FAT, NTFS, Linux Extended and more. This bootable live USB image can be written to external media such as a USB hard drive, USB flash drive or other flash media such as an SD card. Boot from the external media to start up the partitioner.
For Windows users a tool such as Win32 Disk Imager (https://launchpad.net/win32-image-writer) or USB Image Tool (http://www.alexpage.de/usb-image-tool/download) can be used to write the image to a media device.