One of the main reasons I like Klipfolio is because it has simple, lightweight widgets to monitor the memory and CPU usage. Yahoo Widgets have CPU and memory monitors, but they’re heavy memory and CPU consumers themselves. Klipfolio only uses 5MB. I keep the widgets at the very top of the screen so they’re out of the way. You have the option of docking them, which keeps other windows from ever covering them, but I haven’t found that necessary.
Klipfolio has tons of widgets – way more than the ones I’m using – but I don’t need to have RSS feeds or flickr images scrolling across my screen. The system monitors are exactly what I wanted.