I think it is New Zealand, but I don’t know about those other Pacific Islands
Fiji.
It is actually Kiritimati on the Christmas Islands, in Kiribati. Check that site to see how the New Years rolls through.
I never realized that by the time the US celebrates New Year’s the rest of the world already has.
Well, this is just going to make you feel sick:
[spoiler]The pull that same trick every day[/spolier]
On the subject, where does tonight’s intercalary second go? Is it between 23:59:59 and 00:00:00 at every local midnight, or just at midnight UTC?
Technically, the island of Guam is a US Territory and their motto is “Where America’s Day Begins”. Still, it is a “whopping” 4 hours behind Kiritimati.
http://www.timeanddate.com/worldclock/full.html
I heard that there will be a 23:59:60 before it turns over to 00:00:00. Sure will stir upp some confusion at the New Years’ count-down!
Yes, there will. 
My question is - does every timezone put in the intercalary second at midnight, or is it put in at 23:59:60 UTC? In other words, in (say) New York, is the extra second at midnight or 7pm?
Who celebrates it last?
Samoa.
According to Shagnasty’s link it seems to be Samoa.
Isn’t that were Duran Duran recorded Rio?
(If you want extra bad jokes, I have samoa right here.)
Doesn’t the line actually go right through Kiribati? That would make them first AND last!
My BIL was born on Kiribati, Aussie/Brit extraction. Makes for an interesting entry into the “so where were you born?” conversation, even if the general response is “WHERE?!?” 
It used to, but about 12 years ago, they decided to put the entire country on the same day. So effectively, they moved the IDL way to the east. Lots of maps published since have not changed the date line and so are wrong.
The IDL, by the way, has no official status. It’s just a cartographer’s convention, showing dividing line between places that are about 24 hours (give or take a few) apart.