Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
PowerTOP - PowerTOP is a Linux tool to diagnose issues with power consumption and power management.
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.
RMClock - RightMark CPU Clock Utility (RMClock) is a small GUI application designed for real-time CPU...
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...