Though I don't think I'll have Apple banging down my door to design their next iHipTM device, I'm slightly proud of the fact that I turned this:
Here's a really high level description of the workflow I used, with links to all of the open-source software I used:
I used LibreCAD to design each side as a 2 dimensional layout. From that, I imported the 2D dxf files into FreeCAD, to build the 3D mock up you see in the first picture. The mock up was not technically part of the manfacturing pipeline, but it helped me catch a few problems before I milled it. Once I was satisfied, I the imported the LibreCAD files into HeeksCNC to generate toolpaths. Once I had the NC files, I imported into "Pronterface", part of the PrintRun 3D printing host suite. I've mentioned it before, but my CNC is driven by a Sanguinololu board, with a moderately modified version of the Marlin firmware.