Here's a rodent rack I threw together out of parts you can get from your local Container Store.
http://farm6.static.flickr.com/5089/...d5c6276e35.jpg
You will need 4 of the "Grid Stacking Shelf White" found here (currently backordered): http://www.containerstore.com/shop?p...N=&Ntt=shelves. 2 Sterilite "18 gal. Tote Box White": http://www.containerstore.com/shop?p...&Ntt=sterilite. 2 water bottles, elastic bands to hold water, and bungee to hold the totes in place.
I've been running this successfully for over a year now. It can comfortably hold 1.4 rats between the 2 totes. I know a rack can be made for cheaper, and hold more rats, but for someone who's not too handy with tools (me) and has a small collection of bps, this might just be the right thing for you.
Adult male and 2 young females:
http://farm6.static.flickr.com/5206/...281a1e04b7.jpg
2 pregnant females:
http://farm6.static.flickr.com/5287/...e95549abbc.jpg
Any questions? Feel free to ask!