The tzdata update which includes the leap second for Ubuntu just came down the pipe:

Version 2012b-0ubuntu0.11.10:

* New upstream release 2012b:
– Update DST rules for Chile (LP: #948328), Armenia, Samoa, Cuba,
Falkland.
– Fix historic DST rules for Canada.
– Add leap seconds for June 2012.

This is why you need to apply updates regularly, and make sure you are on a supported distro. I’m very curious how mobile is going to handle this, as this will be the first leap second addition any of the major Smart Phone OSes has ever had to deal with.