Jazzcat- I can't get it to link for some reason but in the Cat Rescue section under a thread titled "How you got involved in cat rescue" there is a reply from AVAJOY that has the information about sizes and things like that.
I think the ones that I will make will probably have batting in them so they will be softer. I'm certainly not going to try to hand quilt them but I think as long as you run a few stitches to keep the batting from shifting when they are washed you would be fine. I don't think the kitties will mind if they aren't the greatest looking!! A cheap trick I learned from Grandma was to buy those really cheap blankets and cut them up and use them as batting. They quilt really well and won't ball up too bad in the wash plus you can get a bunch out of one big $5.00 blanket.