Update 20/01-2014: Replicape is now available for sale from the thing-printer store: http://www.thing-printer.com/product/replicape/
Replicape - 3D printer cape for BeagleBone
All the files are available from the git repository.
As of this writing, Rev 3 is the preferred version of the hardware. Rev A3A will be sent in for a small test batch of some 20 boards with assembly.
CircuitCo, the the company that produces the BeagleBones will be in charge of production of Replicape.
Replicape was one of the winners of the cape contest that was held in the end of 2012.
Feel free to contribute to this wiki once you learn something new : )
Meanwhile, a lot of information is spread out on the blog Hipstercircuits.com.