Need a motor driver that can run at the lower voltages? The Didel 2 Motor Minishield can come to your rescue! Use your Arduino Uno (or form factor compatible) board with it to drive a tiny robot around.
The minishield quickly plugs onto an Arduino and runs at such a low voltage that can even run a robot with a single Lipo battery! This tiny shield can handle motor current draw up to 1A per chip so all kinds of motors can be used with it. Bi-directionally control 2 motors and even adjust motor speed on the fly with this handy little board.
The minishield has the all the headers needed to attach it to an Arduino, but keep in mind that you'll need to solder them on. It connects to the digital pin side of an Arduino and includes such features as an on-board ON-OFF switch, Bi-color LEDs indicating motor direction, and a 4-pin Serial Breakout header which adds power & ground lines to serial pins 0 & 1 for exernal devices such as sensors, LCDs, & wireless modules (bluetooth, Synapse, Xbee, etc). The shield uses Arduino pins 4,5,6,7 as the control lines with pins 5 & 6 being used for PWM as well.
Usually the Minishield receives its power from the Arduino below via the Aref pin but if you are drawing a lot of current you'll want to cut the trace at "a" and power the board externally. To do this, solder on the inlcuded jumper wire and connect it to "5V" on the other side of the Arduino board.
Another option is to use the 3 pin external power port available on the left most side of the Minishield if you'd like to power the Arduino using Minishield. You can connect the jumper wire from "b" to the Arduino "5V" or "Vin" header and add power to the Minishield's external power port. If you want a separate supply for the Minishield and Arduino just don't install the jumper wire.