Repetier-Host
The host is the work horse on the pc side. It creates the g-code needed by the printer and sends the data to it.
Learn more abount Repetier-Host for Windows and Linux.
Learn more about Repetier-Host Mac for OS X.
Repetier-Firmware
Each 3d printer needs a fast and reliable firmware to control the hardware.
Learn more about Repetier-Firmware for Arduino based boards.