Woodland Scenics makes a snow product that might work for you.
http://woodlandscenics.woodlandscenics.com/items.cfm/SoftFlakeSnow#SN140
Maybe this will help: http://www.starshipmodeler.com/starwars/ta_probe.htm
Great snow effect that Tony Agustin created for his Probe Droid diorama. :thumbsup
What He said.:thumbsup
Also, I remember reading that the ESB filmakers used baking soda and micro-balloons.
I've been struggling for a while trying to recreate the snow effect on the stop mo puppet, if anybody has any idea's on how best to do this I'd love some input?
baking soda has a tendency to yellow over time.
it looks great at first then looks nasty after a while.
the woodland scenics stuff, that I used for my downed AT-AT here:
http://www.therpf.com/showthread.php?t=38096
it stays nice and white, and can be mixed with the woodland scenics cement, which dries clear, or you can use 1 part white glue and 1 part water and brush on (which also dries clear)
and the flakes are to scale. Doesn't look too big or clumpy
it really is the way to go