Software
- CPU-Z, detects live changes in CPU attributes
- Conky
- frysk - analyzes and monitors system processes
- Ganglia
- GKrellM
- HP SiteScope
- htop
- Iostat
- Motherboard Monitor
- Munin
- Nagios
- nmon
- Sar in UNIX
- SpeedFan
- top
- vmstat
- Windows Sidebar on Windows Vista
- WinBar
- Activity Monitor on Mac OS X
Read more about this topic: System Monitor