A few weeks ago (August 2012) Shinichi Mochizuki has posted a proof of the ABC conjecture. He proves a more general result which has many nontrivial consequences, one being the ABC conjecture.
I am not a number theorist and I have no chance of understanding Mochizuki's arguments (whichh seem algebraic geometric in nature) and I wonder if there is "official" confirmation of their validity.
Update Sept. 5, 2012 A few more details about this announcement can be found here.