Vagrant Cloud is a new service from Hashicorp that strives to make it easy to share Vagrant boxes and to collaborate on provisioned instances together. It's in very early beta, but I have started poking around a little, and it looks interesting. I don't quite know yet how it will work with our extensive custom plugin architecture, but I suspect that this is not an insurmountable problem. Hashicorp is also committed to a freemium model that makes the software stack free (as in speech) and the basic tier of cloud services free (as in beer), so it may be possible for us to have tighter integration with their service without compromising our values. If your curiosity is piqued and you decide to check it out, please do report back to the list with your findings -- it'd be good to know whether this is something we'd want to watch or not.
It does require Vagrant 1.5.1, but I am happy to report that MediaWiki-Vagrant is compatible! :)