Snowflakes are a fun, cheap, easy craft to do on a cold weekend afternoon. You just need paper (I used notebook paper for the one up there) and scissors.
For my snowflake I make a square, then fold in half diagonally then in half and half again. Then cut on all sides, making sure not to completely cut any side (otherwise the snowflake falls apart.) This creates a four sided snowflake.
Of course Martha has great instructions on how to make a six sided snowflake.
And if paper and scissors are just too much work Snow Days is one of the best sites on the web.