Dolverin's Stars
MarlinFirmware/Marlin
Marlin is an optimized firmware for RepRap 3D printers based on the Arduino platform. Many commercial 3D printers come with Marlin installed. Check with your vendor if you need source code for your specific machine.
repetier/Repetier-Firmware
Firmware for Arduino based RepRap 3D printer.
daid/LegacyCura
Read this, it's important! NEW CURA DEVELOPMENT IS HAPPENING AT https://github.com/Ultimaker/Cura, this is the Cura 15.04 archive. Cura 2.1 and newer is on the Ultimaker github.
jcrocholl/Marlin
Reprap FW with look ahead. SDcard and LCD support. It works on Gen6, Ultimaker, RAMPS and Sanguinololu