I've been playing with XNA for the new book (book news coming soon, along with another chapter). As part of this I investigated the use of layers and transparency and what happens if you draw lots of coloured things on top of each other. I ended up with this rather attractive arty looking display which I've made into a clock.
Having decided that the output looked nice, I then reckoned that from a software point of view the code could be a lot better organised. So I went in and tidied things up, re-factored classes, improved the scaling and made the movement of the layers more realistic. And of course the "proper" version looked rubbish.
I'll be making the clock available on verysillygames.com later on. And you can actually see the clock in action here. It is a bit jerky, but it gives you an idea of how it works.
Video: XNA Groovy Clock