Comando, sasd uses white ballast sand, but I recommend either microballoons resin powder ( its used for RC model airplanes) or get snow from Woodland Scenics. You get a much more whiter and truer color to your snow.
TigerII
P.S. sasd's work is great but I thought his snow looked too much like sand.
Achtung Panzer!
Colonel General Heinz Guderian