Ubuntu 11.10 was just released, and I eagerly decided to upgrade my "server' VM to "Oneiric Ocelot". My installation has no GUI, so I could not use the normal tools I'd use to do the live upgrade. So instead, I had to figure out the command line tools to use. Now, this is well documented, but is still worthwhile to repeat.
$ sudo apt-get install update-manager-core $ do-release-upgrade -d
That's pretty much it, just follow the destructions on the screen (oh, and recommended not to do this over an ssh session).