I don't know if a lot of people know about this but you can run virtual machines (some people call them vm's for short) in VMware Fusion 2 or 3 in headless mode. I've just upgraded to VMware Fusion 3. My script (below) has been tested on OSX Leopard running VMware Fusion 3. I find this perfect for running a Linux based server image on OSX.
#!/bin/bash USERNAME=your_username_here IMAGE_NAME=your_vm_image_name_here /Library/Application\ Support/VMware\ Fusion/vmrun -T fusion start /Users/$USERNAME/Documents/Virtual\ Machines.localized/$IMAGE_NAME.vmwarevm/$IMAGE_NAME.vmx nogui