I made a box over the summer using pallets thanks to a design by Zandor. Can you say free wood? The grain looks awesome too.

http://boards.cannabis.com/showthread.php?t=27031

In theory, I can SOG 12 clones in there with 0.5-1.0 oz per plant.

If I did could do it differently, I'd make the door run the entire height not just the top half.