For anyone who missed the announcement, the next incarnation of the Norse god and total bad ass Marvel hero Thor will be a WOMAN!
It was a big move on Marvel's part and one a lot of fans (obviously myself included!) are really excited for. The creators have been asked about it repeatedly and the reasoning they've given is really simple: There's nothing about Thor tied to gender. Thor is a god and a hero, both of those can be men or women so there's no reason that when Oden's son can't fulfill the duties of Thor, the job can't be given to a girl.
Here you can see a teaser preview of the first Thor comic starting Marvel's new heroine, as well as some text free covers and concept art and OMG I am excited! Thor has always been awesome, and girl Thor is no exception.