I have finished the initial design for a new 3D printer cape for the
BeagleBone. Based on the RAMPS and RAMPS-FD, I'm calling the board
"Cape-RAMPS", or CRAMPS. 
At this point, I've just sent out the PCB design to OSH Park, but the
RAMPS-FD folks have been through a couple of prototypes already, the
original RAMPS is obviously a proven design, and I've been doing circuit
board for long enough (since 1986) I think the first version should work OK.
Features & Details:
* 12-24V operation
* 6 Pololu drivers
* 15A driver for heated bed, with dedicated power
* 3 high-current drivers for extruder heaters
* 2 medium-current drivers for fans/lights, always 12V
* 4 Thermistor inputs
* 6 Limit switches (5V tolerant)
* 4 Servo outputs
* SPI and I2C expansion headers (5V tolerant)
* Flexible power options for the BeagleBone (use 'Bone 5V jack, screw
terminals, or add a regulator to generate 5V from 12-24V system power)
* Hardware ESTOP chain
* Stack-through design allows for expansion
I hope to get boards back around the end of the month, and have the
hardware fully checked out and verified by the end of March. I'm hoping
once the design is proven someone will build and sell them inexpensively
(ie: the "direct from China" eBay sellers of RepRap supplies).
Additional resources:
Design files on github:
https://github.com/cdsteinkuehler/bobc_hardware/tree/CRAMPS/CRAMPS
PCB shared via OSH Park:
http://oshpark.com/shared_projects/UQXyTW2Z
RepRap Forum Thread:
http://forums.reprap.org/read.php?13,306594