Top Alternatives to VMware Workstation

VirtulaBox is an open source software to run virtual systems on top of a physical system. Virtual systems are normally used for providing separate environment for each client sharing a single physical system.

QEMU (short for Quick Emulator) is a free and open-source hosted hypervisor that performs hardware virtualization QEMU is a hosted virtual machine monitor.

Parallels Desktop for Mac, by Parallels, is software providing hardware virtualization for Macintosh computers with Intel processors.

VMware Fusion is a software hypervisor developed by VMware for Macintosh computers. VMware Fusion allows Intel-based Macs to run operating systems such as Microsoft Windows, Linux, NetWare, or Solaris on virtual machines, along with their Mac OS X operating system using a combination of paravirtualization, hardware virtualization and dynamic recompilation.

Kernel-based Virtual Machine (KVM) is a virtualization infrastructure for the Linux kernel that turns it into a hypervisor. It was merged into the Linux kernel mainline in kernel version 2.6.20.

Portable-VirtualBox is a free and open source software tool that lets you run any operating system from a usb stick without separate installation.

Microsoft Hyper-V Server is a stand-alone hyper-visor based virtualization product which includes live migration.

MobaLiveCD is a freeware that will run your Linux LiveCD on Windows thanks to the excellent emulator called "Qemu".

Bochs (box) is a portable IA-32 and x86-64 IBM PC compatible emulator and debugger mostly written in C++ and distributed as free software under the GNU Lesser General Public License.

ASG-Remote Desktop integrates a large variety of connection protocols, allowing you to manage Windows, Citrix, Linux/UNIX- and Macintosh systems remotely.