QEMU!

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.

OpenStack OpenStack is a global collaboration of developers and cloud computing technologists producing the ubiquitous open source cloud computing platform for public and private clouds. The project aims to deliver solutions for all types of clouds by being simple to implement, massively scalable, and feature rich. The technology consists of a series of interrelated projects delivering various components for a cloud infrastructure solution.

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. »

The Virtual Environment for secured and comfortable Web Browsing: On the basis of a “Browser-in-the-Box” concept a virtual machine is provided with a reduced operating system and a web browser encapsulated therein. Malware can’t thus penetrate the host operating system and a potential damage in the separated virtual machine will vanish with each start of the browser by returning to a certified starting point. All of that is fully transparent to the user.Protection against malware and data Leakage »

OpenVZ is container-based virtualization for Linux.

UCS Virtual Machine Manager (UVMM) is an easy-to-use and powerful administration tool for KVM. It virtualizes Microsoft Windows, Univention Corporate Server (UCS) and other Linux distributions by centrally providing all the functions for creating and managing virtual instances and hard drives on physical servers.

clearVM, formerly Witsbits, enables you to set up your servers with virtualization and deploy virtual machines faster than ever before. It’s a complete virtualization solution with a self-upgrading hypervisor and cloud-based centralized management, reducing time spent on maintenance to a fraction of what other solutions require. The self-configuring hypervisor comes as a Live CD, removing the need for spending time on configuration or installation and delivering the fastest time-to-deployment.

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.

With the CoreCluster you can create private clouds, like Amazon’s EC2, but based on your own hardware. All what is necessary is some hardware with Ubuntu or Debian operating systems. Users can create theirs own virtual machine instances and manage whole virtual environment, without any hardware reconfiguration. Software supports many additional modules, which extends its base functionality.