TrayStatus shows you the status of keyboard keys like Caps Lock, Num Lock, Scroll Lock, Alt, Ctrl, and more, right in your system tray.
DiskLED is a small tool that displays performance counter data using an animated system tray icon.
https://helgeklein.com/blog/2009/11/how-to-easily-monitor-system-performance-with-the-new-diskled-1-1/