Canonical has recently announced Ubuntu for phones, which is Ubuntu with a specific interface for mobile devices.
Where can I get phones with this version of Ubuntu pre-installed? If no devices are available yet, where can I pre-order one?
As of writing, no 'Ubuntu for phones' devices have been announced. Presumably, Canonical is still working with their partners to deliver some.
If you're interested, why not register to be notified by email as soon as one is announced?
Update February 2013: According to a Wall Street Journal article, Ubuntu-powered smartphones will become available as soon as October 2013. Presumably, this is referencing Ubuntu for phones, and not Ubuntu for Android.
Update July 2013: Ubuntu Edge is a crowd-funded high end phone for enthusiasts and early adopters. They will ship in May 2014 to the backers, assuming the funding goal of $32 million gets reached.
Update August 2013: The Ubuntu Edge campaign ended, raising $12 million in pledges, failing to reach its funding goal. The Ubuntu Edge phone is not going to be, so we're back to waiting for announcements about a more mainstream Ubuntu phone device.