frarose - I wrap them around various kinds of 'boards' and stack them upright. I use foam core - cut into 7 1/2" X 20" from the 30" X 20" sheets. i buy them for $1 at Dollar stores. Others use comic book boards. Makes it very easy to take fabrics out and put them back on the shelf.
fontmomma - the cardboard from Walmart isn't meant for long term storage. It's not acid free, and it can damage your fabric.