If you haven't heard the buzz about Docker but you often need to spin up Linux-based VM's for testing, simulations, etc. then you should check it out. In short, Docker rocks: we use it for testing our Linux-based distros of Revolution R Open. If you want to use R and Docker together, Dirk Eddelbuettel and Carl Boettiger have made it easy with Rocker, and have also provided a nice explanation of Docker itself:
While its use (superficially) resembles that of virtual machines, it is much more lightweight as it operates at the level of a single process (rather than an emulation of an entire OS layer). This also allows it to start almost instantly, require very little resources and hence permits an order of magnitude more deployments per host than a virtual machine.
You can find more info about Rocker at the blog post below, or at the Rocker Github page.
Dirk Eddelbuettel: Introducing Rocker: Docker for R