Admittedly this whole concept is growing old but I was impressed with how easy it is to install Screenlets in Ubuntu, add a collection of fun gadgets, and perhaps even create your own. Screenlets are written using the popular Python scripting engine. While I have had bad luck with similar widget engines in the past, it seems that using common libraries and Python elements has allowed the desktop widget concept to become stable and usable. I have played with these same widgets for several days and have yet to crash anything, or suffer through any error messages.
You can install Screenlets in Ubuntu with a single command in terminal:
sudo apt-get install screenlets
The above will also add all the supporting libraries, and the default "base" of Screenlets to begin using. It's likely that whatever you had in mind comes in the default Screenlet collection. If not, there are few hundred more available from http://www.screenlets.org. There's a large community of widget developers and users out there sharing their ideas.
Once you have installed Screenlets, you can begin adding your widgets using the Screenlets Manager. To access the manager, click System > Preferences > Screenlets. You may also use a "Screenlets Daemon" icon which should appear in the upper right hand corner of your display near the time and volume control slider.
Here you can select a Screenlet, and click "Add" to the right. It should immediately appear on your Desktop. From there you should be able to slide them around by clicking and dragging on them. With a right-click you will find options to change the size of the widget, decide if they should linger on top or underneath your windows, and even "lock" them into place to prevent the accidental sliding around of them. I installed a few common Screenlets and took this screen shot.
These widgets are pretty large on my desktop. The only one I really refer to often is the old analog clock. It's nice to have an analog clock, with the correct time displayed on it. We actually have three analog clocks in my department at the office. They are all battery operated, and each keep their own time. One has recently quit all together, and rather fuss with it I have decided that this clock should display "important times in nerd history". This weeks theme was Back to the Future. I'm waiting for the strike of lightning that will take Marty back to 1985.
Now, go get busy cluttering your desktop with stupid eye candy. It's time well wasted.