I use an under the shelving shelf sideways for their hay rack. I got it for under $10 at Walmart and I just poked holes in my coroplast to hold the shelf in place. The holes are big enough for them to grab the hay but small enough for them not to get stuck in there. I also have a coroplast potty area with aspen and Carefresh under there since they do alot of their business in there while they eat. I tried to find a picture from Walmart to show you what I mean but I couldn't dig one up. I think I have a pic of it in my gallery.
Here's a link to an older version of my cage and a smaller shelving unit. My new one is larger (
http://www.cavycages.com/photos/show...00/ppuser/2563). I hope this helps.