The whole Dock Apps Framework is such a great and nifty idea that one wonders why Apple hasn't incorporated it into the OS. First install the Dock Apps Framework Technology (DAFT) from sf.net. Then, install and run Amnesia. This lovely program displays your memory usage and CPU usage beautifully in real time as an icon in the Dock. When you enlarge the icon, the animation is enlarged, with no loss of quality or information. It has a trivial memory footprint, it's functional, it's pretty, and, above all, it's useful!