What cases are currently available for the Raspberry Pi?
There is a printable card case available here:
I'm currently using it and whilst it isn't as durable as a plastic one, it does the job.
The PI-STACK Raspberry Pi case/enclosure is available on Ebay. It is very heavily constructed in 10mm clear acrylic with solid metal supports allowing access to cables all round including GPIO and camera sockets.
The PI-STACK even has chrome molybdenum steel internal supports!
Independent reviews: http://www.petervis.com/Raspberry_PI/PI-Stack/PI-Stack.html
There are several cases designed for 3D printers at Shapeways. Some of the designs are not yet ready, but you can order most of them.
Here is the canonical list of Raspberry Pi Cases.
(I have a few Pi Sandwiches. They're basic, but fine for the money.)