I often become completely obsessed with photographing one thing for short periods of time. For over a year it was fire hydrants. Then it was mailboxes. Then door frames. For a while I photographed every lock I could find before moving on to bicycle tires and then ultimately discarded cups of coffee on the ground. Sometimes these little obsessions last a week. Sometimes much longer. I never know when they are going to come or go.
A few months ago I became determined to take a picture of water dripping off every day objects. If I recall, it was the first rain after a particularly long dry spell in Portland so my brain naturally gravitated toward the thing that was making me happy at the time, i.e. the world cooling off and watery goodness falling from the sky.
In many ways I consider these little groups of photos to be more like treasure hunts than actual photography. Sure, I try to make an image interesting and all that, but the fun is in finding that thing I want to find more so than making a photo. The image ultimately ends up just being proof, documenting the find, saying to the world, "hey I found it!"
I don't share this kind of work all that often, but I'm considering changing that. It's what I do and it's certainly just as important as all the rest.