I just thought of an amazing alternative to the RepRap motherboard that doesn't need a computer to drive it: the BeagleBoard! This way, you could have it interpret the G-code directly and quickly (as opposed to MakerBot's way of doing that work on the computer and then sending different, simpler commands over the serial lines, keeping the heavy-lifting off of the µController). In my hypothetical setup, the stepper drivers would be run directly from the computer, like how most CNC machines are run (over the parallel port). This also, in the case of the MakerBot, could allow the BeagleBoard to be integrated into the MakerBot with the BeagleTouch screen from Liquidware. This way, you could download, Skein, and print an object all from the MakerBot. Mmmmmm... Standalone MakerBot. Of course, with the RepRap motherboard at $59.00, the BeagleBoard at $149.00, and the BeagleTouch at $258.33, this becomes a bit unfeasible.