VMware Fusion!

VirtualBox is a powerful x86 and AMD64/Intel64 virtualization product for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers, it is also the only professional solution that is freely available as Open Source Software under the terms of the GNU General Public License (GPL) version 2.

Official description: VMware Workstation Pro Lets You Run Multiple Operating Systems as Virtual Machines (including Windows VMs) on a Single Windows or Linux PC. VMware Workstation Pro is the industry standard for running multiple operating systems as virtual machines (VMs) on a single Linux or Windows PC. IT professionals, developers and businesses who build, test or demo software for any device, platform or cloud rely on Workstation Pro.

VMware Workstation Player builds on the industry leading foundation of Workstation Pro, and delivers a streamlined user interface for creating and running operating systems and applications in a virtual machine.

Parallels Desktop gives Mac users the ability to run Windows, Linux or any other operating system and their critical applications at the same time as Mac OS X on any Intel-powered Mac Pro, iMac, Mac Mini, MacBook or MacBook Pro.

Portable-VirtualBox is a free and open source software tool that lets you run any operating system from a usb stick without separate installation. It unpacks and adjusts the paths and configuration of VirtualBox so it will run portably. It will not support bridged networking through the virtualbox network adapter as it is not installed.

Wineskin is a tool used to make ports of Windows software to Mac OS X. The ports are in the form of normal Mac application bundle wrappers. It works like a wrapper around the Windows software, and you can share just the wrappers if you choose.Best of all, its free! Make ports/wrappers to share with others, make ports of your own open source, free, or commercial software, or just make a port for yourself! Why install and use Windows if you don’t need to?

OpenVZ is container-based virtualization for Linux.

Bochs is a highly portable open source IA-32 (x86) PC emulator written in C++, that runs on most popular platforms. It includes emulation of the Intel x86 CPU, common I/O devices, and a custom BIOS. Currently, Bochs can be compiled to emulate a 386, 486, Pentium/PentiumII/PentiumIII/Pentium4 or x86-64 CPU including optional MMX, SSEx and 3DNow! instructions.Bochs is capable of running most Operating Systems inside the emulation including Linux, DOS, Windows® 95/98 and Windows® NT/2000/XP or Windows Vista. Bochs was written by Kevin Lawton and is currently maintained by this project. Bochs can be compiled and used in a variety of modes, some which are still in development. The 'typical' use of bochs is to provide complete x86 PC emulation, including the x86 processor, hardware devices, and memory. This allows you to run OS's and software within the emulator on your workstation, much like you have a machine inside of a machine. For instance, let's say your workstation is a Unix/X11 workstation, but you want to run Win'95 applications. Bochs will allow you to run Win 95 and associated software on your Unix/X11 workstation, displaying a window on your workstation, simulating a monitor on a PC. »

MobaLiveCD is a freeware that will run your Linux LiveCD on Windows thanks to the excellent emulator called "Qemu".MobaLiveCD allows you to test your LiveCD with a single click : after downloading the ISO image file of your favorite LiveCD, you just have to start it in MobaLiveCD and here you are, without the need to burn a CD-Rom or to reboot your computer.

bhyve (pronounced "bee hive", formerly written as BHyVe) is a type-2 hypervisor that runs FreeBSD 9+, OpenBSD, Linux and MS Window desktop (versions Vista, 7, 8/8.1/8.2 and 10), as well as MS Windows Server (versions 2008/2008R2, 2012/2012R2 and 2016 Technical Preview 2 and 3) guests.

Qemu Manager is an easy to use management tool for the open-source QEMU emulator. It has a wealth of features for creating, managing and running multiple virtual machines. It also allows you to run virtual machines within the program itself, giving you quick access to all your running virtual machines.

PC is the fast Java™ x86 PC emulator.Features: - 100% pure Java - Runs as an applet - Modular and customisable - Snapshot capability - Integrated debugger - Bulletproof security

Boot Camp is a utility by that assists users in installing Windows XP, Windows Vista, Windows 7, or GNU/Linux operating systems on Macs. Boot Camp guides users through non-destructive re-partitioning (including resizing of an existing HFS+ partition, if necessary) of their hard disk drive and using the Mac OS X Leopard or Snow Leopard disc to install Windows drivers.