We use a custom open source motor board called the Sangaboard. Currently we use version 3, but we are looking to move to version 4 in the near future. The Sangaboard uses surface mount components and custom boards, the makes it hard to solder your own. If you do make a Sangaboard, you will first need to burn the custom bootloader, before uploading the Sangaboard arduino sketch.
We are looking into a way to sell the Sangaboard. If you cannot get a Sangaboard, you can build your own Sangaboard-compatible motor controller