RepRap Arduino Mega Pololu Shield, or RAMPS for short. It is designed to fit the entire electronics needed for a RepRap in one small package for low cost. RAMPS interfaces an Arduino MEGA with the powerful Arduino MEGA platform and has plenty room for expansion. The modular design includes plug in stepper drivers and extruder control electronics on an Arduino MEGA shield for easy service, part replacement, upgrade-ability and expansion. Additionally as long as the main RAMPS board is kept to the top of the stack a number of Arduino expansion boards can be added to the system.
In RAMPS 1.4, the resistors and capacitors are surface mount to fit more passive components. This does add another set of steps to assembly, but we stuck with larger sizes to make it fairly painless.
This is the bare PCB RAMPS board. You will need electronic components, stepper drivers, thermistors and an Arduino MEGA.
For more information on RAMPS, check out the product page for the pre-assembled RAMPS board.