Yesterday, someone on the Fedora mailing list mentioned gDesklets and I spent a happy couple of hours last night playing with them.
It's a nicely modular way of displaying information on a Gnome desktop. You have "sensors" which extract the information and write it in a standard format and then "displays" which take the information and put it on your desktop. Take a look at some of the screenshots and you'll see the kinds of things that you can do.
The system is written in Python, so that seems to be a good reason to dust down the Python books that I bought a couple of years ago but never got round to reading.