Wooden Potatoes has started an ongoing series explaining the lore surrounding the world of Tyria and the events leading up to Guild Wars 2. He has two parts up so far, hopefully finishing before or right around release. I find this very interesting and informative as I did not play the original Guild Wars and I do enjoy lore to an extent.
Guild Wars 2 Lore: The World
Guild Wars 2 Lore: The Fall of Ascalon