If you want to make your own enclosure, here are the design files I used with the service ponoko.com to make my enclosures:

Enclosure 1: bamboo/acrylic square

Design pros:

• Simple, strong, looks good, clean lines.

Design cons:

• Hard corners and edges means you have to worry about not hurting yourself.
• A few redundant design elements like the holes on the inside pieces that attach to the walls: this was done so lining them up would be easier, but the alternative solution seen in the build photos works great without the holes.
• The burnt edges (dark) are sticky and smell bad for around a month.

Design file mistakes:

• The bottom plate being attached to the rest of it only by long bolts is pretty poor structurally, it should be attached to the sides somehow.
• The hole for the USB cable is too big (not a huge problem, see photos).
• The back wall has holes on the wrong side.
• The bottom plate is engraved where it should be cut.

Build photos:

• Design: http://ljcrabs.blogspot.com/2009/08/monome-enclosure.html
• Build, day 1: http://ljcrabs.blogspot.com/2009/08/putting-together-monome-enclosure-day.html 
• Build, day 2: http://ljcrabs.blogspot.com/2009/08/putting-together-monome-enclosure-day_28.html 
• More photos: http://ljcrabs.blogspot.com/2010/02/monome-40h-m40h-710-top-front-flaws-lit.html

Design files:

•  http://oopha.com/old/monome/enclosure1/

Design files sent to ponoko:

Note: the design file mistakes are not fixed in these, and these files are meant only for reference.

• http://www.ponoko.com/showroom/mp6bZdPafYOUHHXa/monome-enclosure-1-4081

Enclosure 2: rounded corner acrylic stack

Design pros:

• Rounded corners make handling it very nice compared to eclosure 1.
• Bottom plate being on the bottom instead of between the walls makes it feel very solid.

Design cons:

• Looking at it built, the stacked corners are not of very good quality, because the laser cuts wider at the top, and it looks a little jagged, with layers of the stacks not lining up with each other for up to a millimeter difference where they meet. The material chosen being black makes it less noticible.
• The lower-faceplate is too thin to be screwed into without breaking.
• The holes on the layer pieces cannot be made accurately enough with this laser cutter, giving elliptical holes rather than round ones, and needing manual drilling. A better solution might be to forget laser-cutting the holes, clamp the layers together, sand them so they are smooth from one to the next, then glue them and hold in place with a clamp, and glue them to the faceplate as well. Consider using wood because it's easier to work with.

Design file mistakes:

• The holes for the walls are too thin, giving a very tight fit.
• The faceplate button holes are too tight, getting stuck when you push them down. Use the enclosure1 hole sizes instead.

Build photos:

• N/A. There was a lot of re-drilling for holes that weren't cut accurately enough with the laser cutter, followed by giving up and attacking it with glue, followed by the faceplate holes being too thin and therefore the enclosure unusable. I did however, get to hold it to see how the rounded corners feel, they are a big improvement over enclosure 1, mostly not having to worry about stabbing yourself.

Design files:

• http://oopha.com/old/monome/enclosure2/

Design files sent to ponoko:

• http://www.ponoko.com/showroom/mp6bZdPafYOUHHXa/monome-2-4082

Enclosure 3: one piece
An idea I had but never built, a low cost enclosure made from one piece of material.

Design files:

•  http://oopha.com/old/monome/enclosure3/