VMware Workstation 9

there are many different types of software Hypervisors, which allow you to run virtual machines. VMware is one vendor which has Hypervisors,

You could also use Microsoft Client Hyper-V or Virtual PC.

Type 1 and Type 2 Hypervisor Downloads

Type 2 Hypervisor Downloads for Windows OS

VMware Player 5.0 Free Download [FREE]
http://www.vmware.com/go/downloadplayer/

VMware Server 2.0.2 Free Download (discontinued) [FREE]
http://downloads.vmware.com/d/info/datacenter_downloads/vmware_server/2_0

VMware Workstation 9.0 (60 day trial, $199) [EVALUATION]
www.vmware.com/go/downloadworkstation

Oracle Virtualbox 4.0 [FREE]
http://www.virtualbox.org/ 

Parallels Workstation 6
http://www.parallels.com/uk/products/desktop/pd4wl/

Type 1 Bare Metal Hypervisors

VMware vSphere Hypervisor (ESXi 4.1) [FREE]
https://www.vmware.com/tryvmware/index.php?p=free-esxi&lp=1

VMware vSphere Hypervisor (ESXi 5.0) [FREE]
https://my.vmware.com/web/vmware/info/slug/datacenter_cloud_infrastructure/vmware_vsphere_hypervisor_esxi/5_0

Microsoft Hyper-V Server 2008 R2 with Service Pack 1 (SP1) [FREE]
http://technet.microsoft.com/en-us/evalcenter/dd776191.aspx

Microsoft Hyper-V Server 2012 [FREE]
http://www.microsoft.com/en-us/server-cloud/hyper-v-server/default.aspx

Citrix XenServer
http://www.citrix.com/products/xenserver/overview.html

Oracle VM
http://www.oracle.com/us/technologies/virtualization/oraclevm/overview/index.html

Xen Hypervisor [FREE]
http://www.xen.org/

Parallel Server Bare Metal
http://www.parallels.com/uk/products/server/baremetal/sp/

There are many hypervisors available you can use to create VM's. It mainly depends on what your needs are, and what you currently have. Several are free...

There are two types of hypervisors.

Type 1 which run at very close level to the hardware, and so those have the best performance. VMware vSphere (the basic version is free), Hyper-V (included with Windows 2008 servers and Windows 8, also free), KVM (also free) are examples of type 1 HyperVisors.

Then there are type 2 Hypervisors which run inside a normal OS, like Windows 7, Linux, MAC OS etc. VMware Player (free and for personal use), VMware Workstation (similar to the player, but not free), Oracle's VirtualBox (free) are such examples.

You can install many types of OS's as a VM using most of those products.

What are you intending to use your VM's for? Will they be running in a productive environment, or is this more for testing purposes? For productive environments you should use a type 1 hypervisor, not a type 2 like VMware Workstation, as performance will make a big difference.

VMware used to create virtual machines on the virtualization supported servers and desktops. It is not the only software which can give you this ability. If you are using Windows Server 2008, Windows 2008 R2, Windows 2012 virtulization also comes as a role called Hyper-V.
Hyper-V is free as its part of the OS you have purchased but VMware is paid. Both is very good products. Alternatively you may have a look for Virtual PC and Virtual Box products as they are free.
If you are home user don't bother for HyperV or VMware Workstation. VMware also have a product for home users called VMware Player whihc you can create virtual machines on your laptop and desktop computer (if virtualization supported by your hardware). Note: If you have purchased your hardware last a couple of years most likely virtulazition supported. You may check that in your BIOS settings.