MenuMeters is a set of CPU, memory, disk, and network monitoring tools for MacOS X. Although there are numerous other programs which do the same thing, none had quite the feature set I was looking for. Most were windows that sat in a corner or on the desktop, which are inevitably obscured by document windows on a PowerBook’s small screen. The MenuMeters monitors are true SystemUIServer plugins (also known as Menu Extras).
Pros: MenuMeters provides an easy-to-understand and unobtrusive method of monitoring all system performance values and comes with an easy-to-use installer.
Cons: None significant.