MAKE subscriber Clinton Blackmore of Alberta wrote in to share a project he’s working on: NXT I2C Devices for Arduino, which aims to let you control Lego actuators and sensors using a Mindsensors motor multiplexer (NXTMMX) controlled by an Arduino — no NXT brick required.
Oh man. I love the NXT, but I really like the possibilities that this affords. The NXTMMX allows you to connect two LEGO motors to a device that issues I2C commands, and gives you one more port to plug in another NXT device. There is a good tech spec documenting the commands, so there is no reason it wouldn’t work with your microcontroller of choice, by merely connecting four wires and supplying power with a battery pack.