Theoriesonlost.blogspot.com, part of the Dark UFO Lost site.
I like the theory that Jacob is Jack.
1-The name:Jack can be used as a short name of Jacob
2-The visitors of Jacob cabin (Ben, Locke, Christian Shephard, Claire):The future version of jack will have a good reason to need these people Ben cause he is the only one of The Others which will meet jack in 2004 John Locke is the man of faith that make jack came back to the island in 2007 Christian is his FATHER and Claire is his SISTER.
Bonus! Good Lost weekly recaps at 42 Inch Television.