Yesterday, I got some inexpensive fleece-y slippers. They are so warm and soft, but have zero traction; so, I busted out some long-lost puff paint and added my own slip-proof grips. I just painted "don't" on one and "slip" on the other (though you could do anything). I also added little dots on the heels. Presto! Cute slippers with some surprising traction; this would also be great for children's socks.
(p.s. nevermind the bad photos, I used my phone for these).