On the linux side of things, Virtualbox is a much better product than VMWare except for some issues with giving control of USB devices to the VM. It loads faster, and has a coherence mode similar to VMWare Fusion on Mac.
The free solutions are getting much better and can compete with VMWare. Furthermore, I would say the money is not in desktop virtualization, but rather in server virtualization. For this, does VMWare even have a product?