There's a widget as well that provides a more basic view of the info in a neat package. I can't remember the name of it, but I found it in the OSX section of Apple.com, so you can find it there too.
Also, I use an app called MenuMeters. It's a lightweight app that displays basics of your CPU usage, memory, and network in the menubar (sandwiched nicely between Airport and Volume). Google it, it's really all I use and it's very convenient...