The SQUID/SARG VM is a great example. It's configured with two NICs
- one bridged to the 10. network and assigned 10.0.50.20 and the other
set to host-only which provides the Internet access. I can now drop
this VM into any of our sites and simply by setting the proxy in the
Windows clients to 10.0.50.20:3128 full proxying complete with daily
spy-reports are available.
Some apps aren't really suited for a VM, but things like this proxy
VM are a great example. Anything that is self-contained and provides
some significant functionality is a good candidate for VM'ing.