Ronn Kling just published his [2008 IDL Christmas Card](http://www.kilvarock.com/freesoftware/objects/objects.htm). This year's card is a "snownado", a tornado of snowflakes which interact with 3-dimensional objects. The code demonstrates how to efficiently move around many polygons in object graphics. From Ronn's description of the card:
> If you are looking for a way to visualize rapidly moving 3D objects then
> this card may be a good starting place.
Check out previous year's Christmas Cards also, they are all very interesting. [Direct download](http://www.kilvarock.com/freesoftware/objects/snownado.zip).