PowerTOP - PowerTOP is a Linux tool to diagnose issues with power consumption and power management.

SpeedFan - Hardware monitor for Windows that can access digital temperature sensors located on several 2-wire SMBus Serial Bus. Can access voltages and fan speeds and control fan speeds. Includes technical articles and docs.

upower - UPower is an abstraction for enumerating power devices, listening to device events and querying...

Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.

RMClock - RightMark CPU Clock Utility (RMClock) is a small GUI application designed for real-time CPU...

Argus Monitor - Argus Monitor is for monitoring and analyzing the temperature and the health status of the hardware parts of the system.