Wine (originally an acronym for "Wine Is Not an Emulator") is a compatibility layer capable of running Windows applications on several POSIX-compliant operating systems, such as Linux, macOS, & BSD.
A new version of the controller emulator x360ce is available.
dgVoodoo 2 is a free wrapper for old graphics API's for Windows Vista/7/8/10.
Mesa, also called Mesa 3D and The Mesa 3D Graphics Library, is an open source software implementation of OpenGL, Vulkan, and other graphics specifications. Release Notes.
With DS4Windows its possible to emulate a Xbox 360 controller with a Dualshock 4 controller.
DOSBox-X is a fork of DOSBox. It has a focus on accurate emulation of the hardware and many more ways to tweak and configure the DOS virtual machine. You can download it here.
WineD3D for Windows is a DirectX 1-11 to OpenGL wrapper based on WineD3D, which is an almost full implementation of DirectX used in Wine.
With MEMU it´s possible, to play Android games on Windows.
A new version of QEMU, an open source machine emulator for various CPUs, has been released. QEMU is available for Windows (32 a. 64 Bit), MacOS (10.7 recommended) and Android. Here is the changelog.