If you haven't had a chance to check out these videos by WoodenPotatoes (art by Angerina), they are an excellent overview of the Lore of Guild Wars. They begin all the way back before the original Guild Wars and will eventually make it all the way to the current day in Guild Wars 2. So If you're a little behind in your lore, these videos should help get you up to speed.
Only 2 have been posted so far, but I will continue to update this thread as new videos are posted.
Part 1: The World http://www.youtube.com/watch?v=ARZWX51hYYk
Part 2: The Fall of Ascalon http://www.youtube.com/watch?v=X2nznISDkwk