So for people who haven't read the books, a quick summary on brans visions. The children of the forest can see through the eyes of The weir trees (the trees with faces cut into them). Not only can they see through them in the present, they can look into the past. Now with the tower of joy, that opens a few possibilities. They may see the fight outside, see ned and Howland reed enter the tower, and come out with a baby. The tower of joy scene may also possibly be a flashback ( which has only happened once on got so far) of Howland Reed telling the story of what happened. The visions through the weir tree may also include a possible lyanna and rhaegar wedding (tradition in the north to marry in front of a weir tree). Grr Martin has deliberately mentioned that in the past targaryeans have took more then one wife, and that kids from those marriages are legitimate. Therefore jon snow would be the legitimate king.
Also on the r+l=j theory, I was recently watching the second episode, where jon and ned farewelled each other, and ned said 'next time we meet, I'll discuss your mother'. I think this was deliberate from ned. He knew that the next time that he spoke jon would be part of the nights watch, so jon would be bound by oath and wouldn't be able to take his thrown, he'd be safe from danger at the wall (keeping lyanna's dying wish), and not causing chaos that a Legitimate heir to the thrown would cause to robert baratheons claim to the thrown.
