How many types of snow exist? 17!
A great guide to snowflakes from Caltech with high-magnification pictures.
Different snowflake types
This page shows electron-microscope pics of snow crystals,
which are less pretty but more magnified. What is interesting is that they have pictures of faceted snow after it sits
on the ground for a while, so you can see how much snowflakes change.
Ever wanted to know what depth hoar looks like up close and personal? Here it is:
http://emu.arsusda.gov/snowsite/selected/9911.jpg
And this one gets my vote for the weirdest snow crystal ever, looks like a Dali' creation...http://emu.arsusda.gov/snowsite/rimegraupel/13371.jpg