I think the big thing to remember is that the shelters/Humane Societies will probably want the blankets to be washable. When I make them, I cast on (with acrylic yarn), 35 stitches and then knit so that it looks like a big square. Then I bind off and done! Very easy and I am sure the animals and the people at the shelters appreciate them.
Figaro, AKA Debbie
and also on Plurk
Let us so live that when we come to die even the undertaker will be sorry.
Mark Twain (1835 - 1910)