SparkFun has mounted a RFM22 433MHz ISM FSK transceiver module to a shield. What's it do? Let you do a cheap point-to-point (and basic mesh networks) using 433MHz!
You want to move power? We've got the SeeedStudio Relay Shield that'll let the milliamperes of an Arduino-compatible board to control up to 35VDC 70W on 4 separate channels!