Recently went through the process of installing RepRap Firmware on my Due\RADDS setup, documented the whole process in great detail.
Sort of the ‘dummies guide’ version (considering myself the dummy). Mainly blogged it for my own sanity, but thought others may find use of it as well.
Even got support from the Octoprint devs so you can now print off the RADDS SD via the OP web front end, nice!
http://www.akeric.com/blog/?p=3909
Huge shout out to Dan Newman, GroupB, and David Croker from http://fourms.reprap.org for tirelessly answering all my questions.