Came across this fun winter activity at Growing a Jeweled Rose, along with lots of other great kids activities! You can make your own snow with items you most likely already have at home. My boys loved it, especially the part where you make them foam and grow by spraying them with vinegar!
You will need:
-Vinegar, in a spray bottle
Place the baking soda in the tub.
Add some shaving cream and mix it together. The "snow" should start sticking together.
Spray your snowballs with vinegar and watch them foam!