The United States Postal Service issued a commemorative set of four snowflake stamps on October 5th, 2006.  I took these pictures in Fairbanks, Alaska (upper right image), in Houghton, Michigan (lower left), and in northern Ontario (the other two).  Click on the image at left for a closer view.

These stamps are available at post offices across the country.  You can also order them online at usps.com.  At that site, click on Buy Stamps & Shop, then search for "holiday snowflakes" (include the quotes).

My original photographs are shown at left.  They appear blue in these pictures because I illuminated the crystals with blue light (along with some white light and other colors for highlights).  Snow crystals are made of ice, which is clear and colorless, so they are basically the same color as the background.  The folks at the post office changed the colors a bit and digitally "cut out" the crystals and put them on a white background for the stamps.