This is a driver for the low-cost "RFM12" and "RFM12B" wireless transceiver modules from HopeRF. These are available for the 433, 868, and 915 MHz frequency bands and support a simple but effective byte packet format for sending and receiving small amounts of "signaling" data.
The driver is written in C and works on ATmega and ATtiny microcontrollers. Others have ported it to other microncontrollers, such as MSP430 and ARM.
The RF12demo sketch can be used as general-purpose send or receive node, this can be useful while wriitng and testing your own code with this driver.
More info coming soon... overview, examples, etc.