I was downloading torrents in the background while working, so I used Terminal to renice 'Bits on wheels' so I could work freely. Seeing the niced process in Menu Meters' CPU graph gave me this cool (hot) idea: flames, as seen at right.
After installing MenuMeters, open System Preferences, and then click on MenuMeters in the 'Other' section. In the CPU tab, enable 'Display CPU Menu Meter,' and set the pulldown to Graph. Then change the colors to: User Load = red, System Load = yellow, and Nice Load = orange, as seen at left.
And of course, since CPU load will vary as you work, you'll have dancing flames in the menu bar!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060717190317105