Systempal!

CPU-Z is a freeware system profiler (system monitor) application for Microsoft Windows (for all versions from 95 on) that detects the central processing unit, RAM, motherboard chipset, and other hardware features of a modern personal computer, and presents the information in one window. CPU-Z is more in-depth in some areas than the features that Windows XP provides to identify various hardware components, and is thus needed to identify certain components without opening the case, especially the core revision and RAM clock rate. »

Speccy is an advanced System Information tool for your PC, available as installer version and as portable version in 24 languages. It does a quick scan of your machine and gives you a complete rundown of every piece of gear thats in your computer.

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.

CrystalDiskMark is a small HDD benchmark utility for your hard drive that enable you to rapidly measure sequential and random read/write speeds.

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).

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.

WinAudit is an inventory utility for Windows computers. It creates a comprehensive report on a machine's configuration, hardware and software. WinAudit is free, open source and can be used or distributed by anyone. IT experts in academia, government, industry as well as security conscious professionals in the armed services, defence contractors, electricity generators and police forces use WinAudit.

From the makers of CPU-Z, the PC WIZARD is among the most advanced system information programs on the market. PC WIZARD 2008 is a powerful utility designed especially for detection of hardware, but also some more analysis. It's able to identify a large scale of system components and supports the latest technologies and standards. This tool is periodically updated (usually once per month) in order to provide most accurate results.

The Belarc Advisor builds a detailed profile of your installed software and hardware, network inventory, missing Microsoft hotfixes, anti-virus status, security benchmarks, and displays the results in your Web browser. All of your PC profile information is kept private on your PC and is not sent to any web server.

Mac OS X System Monitor and Process Explorer ToolatMonitor is the most advanced monitoring tool for Mac OS X that displays system activity in real-time. It is designed to allow quick assessment of computers state and it is powerful enough to make it a core utility in anyones system troubleshooting toolkit.atMonitor offers a better alternative to Apples own "Activity Monitor" and combines the best of the features of many other existing monitoring utilities. It also adds an extensive list of unique features of its own. In addition to the standard CPU, GPU, VRAM, FPS, Disk and Network info, atMonitor allows interaction with processes, setting up triggers, logging, purging RAM and much more. atMonitor can be displayed in the menu bar, as a stand alone floating window or in the dock icon. »

The BitBar app lets you put the output from any script or program right in your Mac OS X menu bar. And it's completely free. An impressive number of plugins have already been contributed by a wide range of developers just like you, and this site makes it easy to find them.