Free alternative to VMware Workstation.
VMware Player is free, but you cannot create/edit virtual machine settings.
VMware Workstation lets you do it all but isn't free.
That's where VirtualBox starts sounding like a good alternative. VirtualBox is free and lets you do it all. The downside? It's open source and lesser known, so you won't find the widespread support that you'd find with VMware and Microsoft. It does, however, get a constant release of updates and bug fixes, so it's nice to know it's always improving and still being supported.
http://www.virtualbox.org/