There are three widgets from the Yahoo Widget collection that I have been using for a few months that I really like. One is the CPU widget, the RAM widget, and the Local Temperature widget.
There are thousands of widgets that 3rd parties have created, but I tend to stay away from them and just use the ones that Yahoo created. I find the RAM and CPU widget more convenient and less intrusive than having the task manager open. Plus they are very cool. When using Premiere Elements, watching the CPU widget I can tell how hard the computer is working and whether I need to wait before trying the next edit.
http://widgets.yahoo.com/upgrade/
Oh, and the Analog Clock widget is another one I like.