This question might edge on being an IT question, so please bear with me while the IT version of SO is not there yet.
C'mon people, 3 "close" votes a few minutes after the question is up? What's so wrong with it? This might be a little sysadmin-ish, but hey, I really could be a lot more off-topic - and even get upvoted, as long as it's somehow popular - so please don't be so hard-nosed about it.
Take a look at the related questions: This kind of stuff is about our tools, and certainly relevant.
I use a strong PC to run multiple emulated machines (using qemu) in a virtual network as my building and testing grounds to develop a multi-component network oriented software system.
Sometimes, I would like to boot the whole PC into one of the images, for example to further test one of the successful builds. One way would be to have each image in an actual harddisk partition and a GRUB entry for each, but is there a more elegant solution?
Note that in this scenario I would always run only one image at a time, so it's not really about virtualization.