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. It is based on the powerful Arduino MEGA platform and has plenty
room for expansion. The modular design includes spots to plug in
stepper drivers and extruder control electronics. 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 now surface mount to fit more passive components.