Since there is the free VMware Player that allows you to run virtual machines for free on Windows and Linux there is now a ready-to-go Browser Appliance Virtual Machine based on Ubuntu Linux and Firefox:
“The Browser Appliance is a free virtual machine that allows users to securely browse the Internet using Mozilla Firefox.”

The most interesting thing about that is not the pre-installed Linux or Firefox – it’s the idea of making pre-installed available and usable for free. What if we just had something like that for Virtual PC and Windows… what would the impact of that be: giving thousands and thousands of software developers the opportunity to show and demo their products in the wild…
Source: VMware Browser Applicance Virtual Machine