A new Joel's idea from his recent VMWare-related column:
It occurred to me: what if, instead of running a conventional server, you ran your server in a VM? So everything my server does would actually be running in a virtual machine on the server.
Anyway, VMWare has a server product, about which I know very little, but it probably lets you do all this and more and I think it's going to be an increasingly standard policy of good system administrators to build servers as VMs for all but the most CPU-intensive applications.
weissmann and others, what do you think?