The L.A. Times' Hero Complex blog confirms what Marvel Publisher Dan Buckley hinted at last week -- Matt Fraction is indeed taking over the ongoing Thor title.
He'll be joined by an artist familiar with the character, John Romita Jr., who drew the title circa 1998-2000.
Update: So it looks like I jumped the gun a bit; John Romita Jr. is drawing Marvel's Free Comic Book Day book, whose cover is featured above, featuring Iron Man and Thor. The regular artist for Fraction's run on Thor has yet to be announced.
Update: Fraction speaks with Comic Book Resources about Thor.