One of the things I like to do the most is to create graphical user interfaces (and I referring more to desktop programming here than web).
Not just the design but the whole stuff. It is the way you have in programming to transform something complex in an easy and pleasant tool to use.
We all know how to do some scratches in a paper to come up with the looks for a new interface. Some time ago I was told about paper prototyping and it is a nice, fast and easy way for testing an interface for usability.
Here are some images and a book about the subject. This article is also pretty good and you can find a number of videos of people demonstrating how it’s done on YouTube.
Give your shot on paper prototyping!