Just checked the Minecraft status, the Login, Session, and Website have been down. View this for seeing how long each have been, and if they are brought back up or down: http://xpaw.ru/mcstatus/ Also, this is being caused by people DDoSing Minecraft due to the EULA change.
This describes what Mojang is doing, and people's reaction. http://www.change.org/petitions/mojang-change-the-eula If you think this is all wrong, just give your say and sign it, but at least read the arguments from both sides.
mojang is updating there login system so for all premium servers (non-cracked server) no one willl be able to join servers unless its a cracked one