Team Fusion

Ever wonder where your virtual machines are kept? The default location for non-Boot Camp virtual machines is /Users/${USER}/Documents/Virtual Machines. Boot Camp virtual machines are kept in /Users/${USER}/Library/Application Support/VMware Fusion/Virtual Machines. You can also locate a virtual machine by ctrl-clicking on it in the Virtual Machine Library and selecting "Show in Finder".

Yet another way to find virtual machines is to use the fact that they tend to be quite large. Simply look for where your disk space is being used, perhaps with a tool like Grand Perspective or with a regular Finder search.