I wanted to try out the Mindstorms NXT2 with raw I2C, but this involved making a homebrew 6-pin connector because Lego use a proprietary type to avoid kids sticking them into your Ethernet wall socket. Some Minicraft cutting and epoxy sticking later and on the second attempt I had a working breakout cable.
The little board cost a couple of pounds on eBay and has an I2C analogue-to-digital converter with a light dependent resistor, thermistor and variable resistor for testing. Programming blocks for Mindstorms are easily downloaded and installed to the Lego software.
The NXT is reading ambient light and displaying an 8-bit value on-screen.