http://img395.imageshack.us/img395/962/casecj5.jpg
Not pictured: 2-fan Blow-through power supply.
Just have to go through and tape up all of the holes that aren't an exit.
Yes, my airbox is Tupperware. I needed something that would seal, yet pop off when I wanted it to. So I RTV'd the lid to the case, cut my holes, and bam.
I do allot of woodwork out there, huge amount of dust. I may change to larger Tupperware, and automotive panel filters.