SMARTReporter warns of ATA hard drive failures before they happen by periodically polling the S.M.A.R.T. status of the drives. S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) is a technology built into most modern hard drives that acts as an "early warning system" for pending drive problems. SMARTReporter can notify you of impending drive failures by sending email messages, displaying a warning dialog, or executing an application. The current status of your drives is always displayed through the customizable menu item.
X Resource Graph (XRG) is a system monitor that shows graphs for CPU usage, memory usage, battery status, machine temperature, network usage, disk usage, current weather, and stock market data. It is designed to use as little overhead possible while showing a lot of information about the resource usage in a nice interface.
Nageographer is a graphical utility to aid in positioning icons on the status display maps in Nagios (a network monitoring tool). Nagios, as shipped, requires you to enter coordinates for each icon you want displayed on the status map. This utility lets you drag the icons around where you want them and will save your coordinates back to the config file for you.