XWidget!

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. »

Conky is a free, light-weight system monitor for X, that displays any kind of information on your desktop. Originally a fork of Torsmo, Conkys torsmo-based code is BSD licensed. New code in Conky has been licensed under the GPL 3.0.

This is a port to OS X El Capitan 10.11 of MenuMeters by Alex Harper.

Plasma Workspaces is the umbrella term for all graphical environments provided by KDE. Plasma separates components into "data engines" and their visualization counterparts. This is intended to reduce the total programming effort when there are multiple possible visualizations of given data; and to make it easier for the data engine and the workspaces to be written independently. Currently there are three workspaces being developed: Plasma Desktop for traditional desktop PCs and notebooks, Plasma Netbook for netbooks, and Plasma Active for tablet PCs and similar devices. »

GeekTool is an application for Mac OS 10.6+. It lets you display various kinds of information on your desktop via 3 default plug-ins:

8GadgetPack makes it possible to use gadgets on Windows 8 / 8.1 / 10.

MiniUsage displays various data like CPU usage, amount of network flow, battery status and process names which uses much CPU time in a menubar. It takes little space and can display various data, so it's suitable for notebook.

Monitor numerous OS X statistics including: CPU activity System load over time Network bandwidth and activity Memory activity and usage Battery & wireless signal strength Disk usage Current time and date Compact, clever & fully customizable user interface Presents information both graphically and with text Beautiful on Retina display Fits in perfectly with the new system appearances Save & load custom appearances Minimizes impact on system performance View data on the desktop, in the menu bar or Dock Show & hide windows using system hotkeys »

GKrellM is a single process stack of system monitors which supports applying themes to match its appearance to your window manager, Gtk, or any other theme.

Moo0 SystemMonitor is a smart free program that shows what is going on with your computer. The program uses a minimal amount of ressources, and you can learn from it where your computer "hangs". You can see your computer under many perspectives, and with the features you can diagnose your computer. You can have as many features as you want open and have them in the way that fits you best on the screen.It could be installed or also have a portable version.

Theme Widgets has eight small apps that run on your PC desktop. The apps cover different tasks such as: clock, calculator, weather, notes, calendar, timer, stopwatch and a whiteboard. This will hopefully grow over time.

This little application displays system information on your desktop in a similar way to some other desktop information tools. Unlike others, this application looks like wallpaper but stays resident in memory and continues to update the display in real time. Uses very little memory and nearly zero cpu. Perfect for quick identification and walk-by monitoring of production or test server farms. Everything is customisable including language.

Nerdtool allows you to display many things directly on top of your desktop; weather reports, headline news, and system vitals are just a few uses.

Download a multi widget toolbox. Use an elegant and clean display with one-click access. Use widgets, including Countdown Timer, Logbook Calculator, Month view Calendar, Rich Notes Editor, Slides Whiteboard, Weather Forecast and a Stopwatch Timer. Start the widget with windows and don't worry about turning it on. Enjoy creating custom transparent themes. Change the colors, fonts, contrast and opacity of the widgets. Have great-looking widgets with a super clean and minimal layout. Move around the screen very easily. The widgets snap to a default grid on the screen. They are also resizable widgets with super easy preset sizes. »