I've actually heard this question asked a lot in a bunch of different forms, and (to me) it basically comes down to: How do I use virtualization to provide additional security to processes?

The advantage of virtualization is that it provides a very strong statement of security (if a lesser statement of performance). On the other hand Jails/Containers (see LXC) have a strong statement of performance and a lesser statment of security.

For you, I'd recommend checking out Linux Containers, because it does provide more protection than just a process, but is faster and uses less resources than a whole VM.