The type of motor driver you need depends on the type of motor you have.
Stepper motor driver: lots of choices for all the stepper motors.
Most RepRaps use stepper motors.
DC motors are rarely used for RepRap purposes, but one driver exists: DC Motor Driver 1 1
- brushless DC motors
- servo motor drivers
Other kinds of motors and the specific electronics required to drive each kind are listed at Open Circuits: motor driver.