I let my sewing group know that I was making dog/cat beds and then they donated fleece and cut up batting that was cut off of quilts after they were quilted. Sewed up the fleece into a pillow case style; started stuffing about 1/3 of the bed, then sewed across side to side, continued stuffing to about 1/3 again, sewed, and on last part stuffed and sewed the last seam.
The shelter loved them.