Since the weather forecast for today was something like "WE'RE ALL GOING TO SPONTANEOUSLY COMBUST," I figured it would be a good idea to get up at the time I would be getting up if I was working in an office building like regular people and go take some photographs down at the Patapsco River.
Now that I've subjected you to a horrible introductory run-on sentence, let's get down to business.
I generally keep my camera in the basement, which stays at a cool 68 degrees Fahrenheit. When I suddenly subject my camera to intolerably hot and humid conditions, such as those currently plaguing Maryland, all glass surfaces immediately fog up. This is a basic principle of heat transfer and its relation to the physical properties of water, something I was taught in three separate classes over my college career but still somehow have difficulty recalling off the top of my head. But we're talking about photography, not engineering, so who cares!
Despite this being somewhat frustrating, it creates an effect that you can use to your advantage in photography. If you rub the condensation off the center of your lens using a cotton or microfiber cloth, but still leave some on the edges, you can obtain an interesting halo effect, as the condensation will cause an interesting diffuse glow around whatever light sources you have. Rubbing some of the condensation off will allow people who see your photo to actually identify what's going on.
In this image, the sunlight is almost directly above, causing the glow at the top of the photograph, while enough condensation was rubbed away to make it quite clear that I am photographing a bridge and not, say, a pile of toothpicks or the crystal lattice structure of a microscopic piece of quartz.
This principle works also in the wintertime. Some years ago, I figured out that exhaling onto a camera lens also fogs it up, and came up with this photo during an ice storm.
Go on out there and try it yourself! However, I don't anticipate that this will work very well (or even at all) with a regular point-and-shoot camera, due to the tiny size of those lenses. If you do succeed with one, let me know! And I'd love to see the photos you take!