"Snowflakes - A Thematic Approach" provides K-12 teachers with a flurry of 
ideas for using snow to deliver interesting and exciting interdisciplinary 
instruction perfect for the winter season. 
http://www.wsanford.com/~wsanford/exo/snowflakes.html

Make-a-Flake
http://snowflakes.lookandfeel.com/

For photographs of H2O molecule-ice crystal models, see
http://www.wsanford.com/~wsanford/gr8ps/snowflakes/ice-xls/