Paraphrased/edited/slightly updated form of: http://mike.teczno.com/notes/disposable-virtualbox-lxc-environments.html
Download an Ubuntu Server ISO (http://www.ubuntu.com/download/server)
Create a new VMWare virtual machine, select boot from the ISO with 2 NICs configured as "Share with My Mac" & "Private to my Mac" respectively. During the creation of the Ubuntu VM there will be a page to select installed software, select "OpenSSH server".