This is a case for a PolargraphSD machine. Which is essentially a arduino mega, with a polarshield stuck on it, and a 2.2" LCD touchscreen and a pair of stepstick motor drivers stuck on that. The case consists of five parts.
This version has been superseded by http://www.thingiverse.com/thing:32377 which is for the polarshield v1.1.
Part 1 is the main piece, a tray that holds the electronics.
Parts 4 and 5 go on next and support the LCD screen.
Part 2 goes on next and covers the main exposed part of the circuit, and the stepper drivers.
Part 3 goes on last and frames the LCD.
There are two versions of parts 1 and 2, made for differently sized USB ports. The ones with b on the end are for a big USB-B socket like on a regular Arduino Mega. The ones with m on the end are for a smaller mini-USB socket boards that I more commonly use - Freaduino Megas mostly - they use the low-profile mini-usb connections. I think they are the best megas money can buy. (note I've just modified the filenames as of 18th August 2012, so if you downloaded a b before then, you will have got the mini version. Confusing, I know.)
I use five 15mm M3 bolts to secure it. I print this in ABS on my little huxley. It seems to take hours.
The polarshield itself is a separate thing that I will publish once I get the design pinned down a bit more smartly. In the meantime, the eagle layouts are available at http://code.google.com/p/polargraph/source/browse/#svn%2Fhardware if you do need them.
The LCD is a ITDB02-2.2, it has a built-in SD card slot. Although it seems profligate to have a touch-screen on this, it works out cheaper than making my own buttons+lights panel with SD slot. And now there's no going back, baby. I wish I had some dials though.
The sprockets for the beaded cord are here: http://www.thingiverse.com/thing:19690
More about this at www.polargraph.co.uk.