At "long last"[*], there'll be a leap second again this year at the end of December, according to the email I just received!
So 2008-12-31T23:59:59 (UTC) will be followed by 2008-12-31T23:59:60.
Go and spread the word!
...I'm such a geek.
[*] Leap seconds have historically come roughly every 18 months, but it's been three years since the last one, and the last one before that was seven years earlier. (They don't come regularly since they depend on the earth's rotation speed, which is a bit irregular and hard to predict much in advance.)