I needed to run an appliance inside VMware Fusion on my Mac, the appliance was in OVF format. VMware Fusion currently does not support this format and requires you to convert the image with a tool called ovftool which can be downloaded at the following location: http://communities.vmware.com/community/vmtn/vsphere/automationtools/ovf
Conversion is as simple as:
./ovftool "source.ovf" "target"
Optionally you could use parameters that are described in full detail when running ovftool –help. What remains is importing the created .vmx into Fusion, that’s it.