Hardware Lister - lshw (Hardware Lister) is a small tool to provide detailed information on the hardware...
HDD Led Indicator - This is a hard disk activity monitoring tool.
iStat Menus - "An advanced Mac system monitor for your menubar."
DriveGLEAM - DriveGleam is a free app that installs a handful of activity indicators as icons in your system...
Speccy - Speccy - find the details of your computer's specs. Great for spotting issues or finding compatible upgrades. Download the latest version free.
Atlas Hard Drive LED - Atlas Hard Drive LED is a system tray utility program that allows the user to always be aware of whether their hard drive is reading or writing. The system tray icon will change to the color red when the selected hard drive is processing.