The Adafruit 16-Channel 12-bit PWM/Servo Driver does not need a motor shield. It is a great solution for driving a lot of servos or LEDs. In theory, you can chain up to 62 of them for a total of 992 PWM outputs.
The Adafruit MotorShield
will handle up to 4 DC motors or 2 steppers, plus up to two servos.
For maximum fun, you could combine the Servo Driver and the MotorShield together, giving you DC motors, steppers and lots of servos.