While browsing around today I found a simple internet game that can produce some neat results. Better Homes and Gardens offers a similar program, but requires a lot of personal information before you can make a snowflake.
At Zefrank, you can make a rotating 2-or 3-D snowflake. Try making changes while it's moving!
One of my Christmas decorations, not a snowflake I made, but pretty.
If you want to make real paper snowflakes, this site has patterns that guide your cutting.
Kinderart offers templates to make specific patterns, along with a few recommended books.
Want to know more and need some hands-on help? Google Books lists 1013 titles about making snowflakes!
A lovely Japanese story about a snow fairy can be found here.
So if you're covered in snow today, or expecting some flurries as we are, these actitivies should give you and your young ones a few things to do. And don't forget to make some snow ice cream!