Virtualizate

http://en.wikipedia.org/wiki/Operating_system-level_virtualization

http://www.freevps.com/

http://linux-vserver.org/Welcome_to_Linux-VServer.org

http://openvz.org/

http://bochs.sourceforge.net/

http://bulma.net/impresion.phtml?nIdNoticia=2094
http://www.linuxvirtualserver.org/

XEN http://www.xensource.com/about/pages/unify.aspx o http://www.xensource.com/Pages/default.aspx

VMWARE http://www.vmware.com/es/

QEMU http://fabrice.bellard.free.fr/qemu/

VITUOZZO http://www.swsoft.com/es/products/virtuozzo/ (este creo que no tiene nada free)

VIRTUALBOX http://www.virtualbox.org/

PARALLELS http://www.parallels.com/ para MAC ¿?

VIRTUAL PC 2007 http://www.microsoft.com/windows/products/winfamily/virtualpc/default.mspx

Your source for VMware and Virtual Box images

http://vmvilla.com/

PROMOX
http://pve.proxmox.com/wiki/Main_Page
OpenNebula
http://www.opennebula.org/doku.php