Let me get you up to speed-
So, according to sources on the internet, True Blood's Alexander Skarsgard was said to be cast as Thor, and I can see why, but those rumours were nullified when we found out Alexander would not be casted as Thor. We then find out that Chris Hemsworth was officially cast as Thor. Now most recently, from ComingSoon.net, we find out that (Alexander Skarsgard's Father)Stellan Skarsgard, will be joining the cast of Thor. In what capacity though, we don't know.
We'll have more as it develops.