I use drapery fabric all the time. I take the fabric to the laundamat and wash in a front loading washer and dry.

You can also use sheets.Just buy the size you need,and you can co-ordinate them or match them.lots of choices there.
kathi

Thank you for the ideas. I had'nt thought of sheets or drapery fabric. Will restart the hunt now :)
-veena

Or you can purchase extra width cotton fabric, called Fat Backs:

http://www.christianlanequilters.com/home.html

I've always used sheets.

Here is a link that might be useful: Christian Lane Quilters

I made a duvet cover recently out of a heavy cotton that had some weight to it. I like the feel of weightier blankets on me, but some people don't. So remember to keep that in mind when you pick your fabric.

Also, I'd stray away from any fabric that was slippery so that your blankets don't slide off in the middle of the night.