Dexter Industries (who previously developed BrickPi, a LEGO-Mindstorms interface board) are bringing out GrovePi. GrovePi is an add-on board that plugs into the GPIO pins and allows you to use Grove Sensors from SeeedStudio. These are little modules with a cable and the GrovePi has lots of sockets into which you can plug the cable. I’d love to get my hands on one of these as I think it presents a great way to easily get the Pi interacting with the real world without a lot of messing about with breadboards and/or Arduino boards.
The GrovePi itself uses an Arduino chip and interface to work, but because it’s all mounted on the board I expect the interface to be pretty seamless. Documentation is going to be vital here! You can pre-order a GrovePi for $23.99 which I think is stunningly good value. Another thing I particularly like is that they’ve used a long-pin GPIO header meaning you can stack other boards on top of the GrovePi.