I have a number of different hobbies but my main one would definitely be photography.  Another of my hobbies it to scour thrift stores and other shops for props to use for my photos.  One of the items I'm always on the lookout for is coloured glass cups and bottles.  

In this photo I took some of that coloured glass and put it on my front step.  It was a sunny day so the light provided for some pretty neat and colourful shadows. It was fun trying to capture these shadows.   If it's sunny in your part of the world today, see what kind of shadows you can create and capture.  If not, see what you can create with artificial light sources to show us your hobby.