Instructables user Mrballeng wanted some waterproof snow boots, but wouldn't use them enough to invest in anything commercial. His solution? He sprayed down an old pair of boots in rubberized undercoating.
Using a Rust-oleum rubberized undercoating on the boots kept his feet dry and warm through a day of sledding in the snow. He notes the coating started to crack a little by the end of the day, but as a quick, albeit dirty solution it works in a pinch. Clearly you wouldn't want to do this on a new pair of boots or shoes, but if you have an old beat up or uncomfortable pair lying around and need the occasional unfashionable snow boot, this might suit your needs.
Improvised Sledding Shoes | Instructables