Alot of folks are running cases like these:
http://amzn.to/mzWGQRThey can be picked up for about $35 and are perfect for open air mining. It will be hard to beat that price point.
That same company offers a stackable open air case that I absolutely love. It runs about $50 bucks and I can stack as many rigs as I need on top of each other. Check it out here:
http://amzn.to/jPdb7eDarn, I bought it from them (myopenpc) off ebay instead of amazon, and payed $43.