Hi greenpixies,
I'm a newbie too! Someone else on the forum told me about it. 
You should be able to get it at any feed/tractor store. Stall dry is used for all kinds of animals, including horses. One of the ingredients in it is DE. I paid about $17 for a 44# bag, and it lasts awhile. It looks like dark sand, you just sprinkle it in the coop and run and it absorbs odors, ammonia and moisture. My coop/run doesn't smell at all! It's also 99% dust free, so you don't get all that dusty powder like you do with pure DE. I usually sprinkle DE first, and then stall dry over it every few days. 
I don't think I'm crazy about the DE though, and once I run out, I'm going to go without it for awhile and see how I feel. 
I love stalldry! And it's so cheap!