MinimizeToTrayTool is a freeware open source utility that allows the user to minimize any application to the windows tray.
WindowTop enable you to pin any window on top, enable window transparency, even click through transparent window, set window dark / read mode, shrink the window to small size and more. Read & See more: WindowTop.info
UltWin creates an interactive scalable view of the desktop, the Desk View. UltWin creates mini-windows on the Desk View to represent desktop applications and Windows 10 apps.
MaxTo is a window manager that allows you to define screen regions that windows automatically maximize to, for pixel-perfect window arrangements. Make the most of your screen estate. Quickly move windows using hotkeys.
Sawfish is an extensible window manager using a Lisp-based scripting language
awesome is a tiling window manager initialy based on a dwm code rewriting.
An extensible window manager for the console.
Free and open source textmode window environment