This motor shield has been discontinued for a while and replaced with v2.0 Motor Shield, but if your project doesn't require the higher peak current and you want to save a couple bucks, we still have some available.
Arduino is a great starting point for electronics and with a motor shield, it can also be a nice clean platform for robotics and mechanical projects. Here is a design for a full-featured motor shield that will be able to power many simple to medium-complexity projects.
2 connections for 5V 'hobby' servos connected to the Arduino's high-resolution dedicated timer - no jitter!
Up to 4 bi-directional DC motors with individual 8-bit speed selection (so, about 0.5% resolution)
Up to 2 stepper motors (unipolar or bipolar) with single coil, double coil, interleaved or micro-stepping.
4 H-Bridges: L293D chipset provides 0.6A per bridge (1.2A peak) with thermal shutdown protection, 4.5V to 25V
Pull down resistors keep motors disabled during power-up
Big terminal block connectors to easily hook up wires (10-22AWG) and power
Arduino reset button brought up top
2-pin terminal block to connect external power, for seperate logic/motor supplies
Tested compatible with Mega, Diecimila, & Duemilanove