Lm-Sensors!

The Open Hardware Monitor is a free open source software that monitors temperature sensors, fan speeds, voltages, load and clock speeds of a computer.

SpeedFan is a program that monitors voltages, fan speeds and temperatures in computers with hardware monitor chips. SpeedFan can even access S.M.A.R.T. info and show hard disk temperatures. SpeedFan supports SCSI disks too.

HWMonitor is a hardware monitoring program that reads PC systems main health sensors : voltages, temperatures, fans speed.

Core Temp is a compact, no fuss, small footprint program to monitor CPU temperature.

SidebarDiagnostics - A simple sidebar for Windows desktop that displays hardware diagnostic information.

Real Temp is a temperature monitoring program designed for all Intel single Core, Dual Core, Quad Core and Core i7 processors. Each core on these processors has a digital thermal sensor (DTS) that reports temperature data relative to TJMax which is the safe maximum operating core temperature for the CPU. As your CPU heats up, your Distance to TJMax will decrease. If it reaches zero, your processor will start to thermal throttle or slow down so maximizing your distance away from TJMax will help your computer run at full speed and more reliably too. »

MHDD is the most popular freeware program for low-level HDD diagnostics.

Stress Terminal UI or “s-tui” is a terminal tool designed to make it possible to stress test and monitor your Linux box. It is a TUI (no X server required), showing your CPU temperature utilization frequency and power consumption in a graphical way.The software has integration with Linux stress tool "stress". This makes it possible to monitor your CPU statistics under heavy load. Since the tool runs in the terminal, it is possible to use it over SSH. This is useful for headless servers, small single board PCs such as Raspberry-pi, or simply if you prefer using the terminal. »

WinBar is a free and compact program that lets you monitor your system and provides easy access to frequently used controls. WinBar will run on Windows 2000 and newer operating systems and is available in 32 and 64 bit flavors.

Personalize your experience with state-of-the-art real-time overclocking*. Used by world record setting overclockers across the globe, AMD OverDrive™ gives you unprecedented control over your processor, memory and chipset to push the performance envelope further than ever before.

RightMark CPU Clock Utility (RMClock) is a small GUI application designed for real-time CPU frequency, throttling and load level monitoring and on-the-fly adjustment of the CPU performance level on supported CPU models via processors power management model-specific registers (MSRs). In automatic management mode it continuously monitors the CPU usage level and dynamically adjusts the CPU frequency, throttle and/or voltage level as needed, realizing the "Performance on Demand" concept. Notice: RMClock is different than CPU RM, those are two very different pieces of software designed to do different things. »

PassMark DiskCheckup allows the user to monitor the SMART attributes of a particular hard disk drive. SMART (Self-Monitoring Analysis and Reporting Technology) is a feature on a computer's hard disk for providing various monitoring indicators of disk reliability. If SMART is enabled on a hard disk, the system administrator can receive analytical information from the hard drive to determine a possible future failure of the hard drive.

Monitoring temperatures and status of system components such as CPU, GPU and hard disk drive, fan speeds

Active@ Hard Disk Monitor is a disk utility that checks and monitors the status of your hard drives to help prevent data loss. The system is based on the Self-Monitoring Analysis and Reporting Technology (S.M.A.R.T.).