We are planning on releasing a IO-board with a Atmega2560 onboard and mountingholes and gpio-contact for a Raspberry Pi. It has 4 RS232, 1 RS485/422, 8 digital input and 4 relay outputs.
A optimal solution if you want to build your own dorraccess system och some kind of a controller for buildingautomation. Communicate with the Atmega through UART.
Please read more about the project at http://www.expansionboard.org