There are four options for using VMs in Linux. The three open source options are KVM, XEN, and VirtualBox. Commercially, VMware supplies a virtual engine that can be hosted in Linux and an executive that can run VMs.
VMware has been supporting VMs longer than anyone else. They support Unix, Linux, Mac OS X, and Windows as hosts and Unix, Linux, and Windows as guest systems. For commercial use, VMware Player or VMWare Workstation are the two best choices you have.
KVM and VirtualBox are the two most popular VM engines for Linux. KVM delivers better performance, but it requires a CPU that supports virtualization (Intel VT-x). Most modern Intel and AMD CPUs support these features. VirtualBox has the advantage of being ported to Windows and Mac OS X, allowing you to move a virtual machine to another platform easily. VirtualBox does not require VT-x support, making it suitable for legacy...