Open Hardware Monitor!

Rainmeter is a desktop customization platform. Through Rainmeter, you can enhance your Windows computer at home or work with skins: handy, compact applets which float freely on your desktop, much like Windows Sidebar gagdgets, or dashboard widgets for the Mac. Rainmeter skins provide you with useful information at a glance. Its easy to keep an eye on your system resources, like memory and battery power, or your online data streams, including email, RSS feeds, and weather forecasts. Many skins are even functional: they can record your notes and to-do lists, launch your favorite applications, and send your tweets to Twitter - all in a clean, unobtrusive interface that you can rearrange and customize to your liking. »

GPU-Z is a lightweight utility designed to give you all information about your video card and GPU. The application supports ATI and Nvidia cards. The information provided includes GPU model, BIOS version, clock rate, memory size, etc as well as live readings of card sensors for temperature, voltage and current.

AIDA64 is a system information, diagnostics, and auditing application developed by FinalWire Ltd., that runs on Windows, Android, iOS, Windows Phone and Tizen operating systems. It displays detailed information on the components of a computer. Information can be saved to file in formats such as HTML, CSV, or XML.

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.

iStat is a series of system monitor apps. It's available in different versions: iStat Menus, iStat for iOS and iStat Server as a companion application to the iStat for iOS app that lets you remotely monitor your computers (free for Windows and Mac).

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

Hardinfo is a system information and benchmark tool for Linux. It shows detailed system info, including hardware, environment, and kernel. It can use lm_sensors and ACPI for temperature and battery information. It also has four CPU banchmarks and two FPU benchmarks. It can generate reports as well.

cinnamon-cpufreq-applet - Port of Gnome 3 CPUFreq applet to Cinnamon - with some fixes.

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. »

smcFanControl is the perfect application for all those Macbook owners getting burned by their hot-running Macbook.This Mac application allows you to control the speed of the fan in your MacBook so you can avoid it running hot.

Lm-Sensors is a free and open-source application that provides tools and drivers for monitoring temperatures, voltage, and fans.

3C Toolbox is the comprehensive toolbox to save battery, tweak, tune, backup, secure and monitor any Android devices running any ROMs, any kernels.