Snowman Paint looks like a great shortcut to actually rolling all that snow and finding accessories like carrot noses: just draw the snowman on a natural heap of snow, much easier! Or you could use the eight spray-on snow paints to draw faces and clothing on your snowman. I'm assuming that the paint will not leave permanent marks on sidewalks, or maybe that's part of the fun, seeing the designs that watery paint muck leaves behind.
$18 for a set of 8 colors at PlumParty.