Our layout used to be indoors and only came out at Christmas time. Eventually when I started getting more into realistic modeling and a bigger and more elaborate layout, I wanted to try a snowy look. But I wanted something that would be easy.
My mom had some quilt batting she wasn't using...well she wasn't using it after I got to it /DesktopModules/NTForums/themes/mls/emoticons/hehe.gif
So I cut up some to fit around the buildings. Looked good enough to me. Might be kind of funny, and not very realistic for a permanent layout, but it worked great for a removable Christmas layout.
Looking online to give some links to quilt batting, I stumbled across this stuff that is used for fake snow:
Buffalo Snow
Interesting stuff, looks a lot like quilt batting I used.
But then if you move outside where it snows, you can have scenes like this: