The fluorescence and occasional phosphorescence of some minerals under ultraviolet light has fascinated me since I was a child, and I now have both short-wave and long-wave UV lights and a small fluorescent mineral collection. It's fun finding different things that fluoresce… Powder laundry detergent, many types of consumer packaging, and scorpions will all fluoresce.
Here are some interesting UV links that I recently found:
This UV lighting website has animations of morphing mineral specimens under different light wavelengths and an amazing photograph of a completely fluorescent mine interior. The website doesn't say, but I'm guessing that the mine interior is of Calcite (reddish-orange) and Willemite (bright green) under short-wave ultraviolet light, possibly from the famous (at least to mineral collectors) Franklin and Sterling Hill mining district in New Jersey.
Here's a list of minerals and the colors that they fluoresce under short-wave and long-wave UV light.
Here are photographs of flowers in ultraviolet, and it is quite interesting to see how different these flowers look in UV light, even the commonest of flowers like a Dandelion. Unlike humans, a number of insects can see in the ultraviolet part of the light spectrum, and flowers, even those than look solidly-colored to human eyes, can be marked with bold ultraviolet bull's-eyes and bands to both guide in pollinators and in some cases warn off potential flower eaters.