Minecraft News: All Servers Down (OpenSSL bug)
Mojang shut down all of their servers because of one of the biggest OpenSSL bugs ever in history !
The servers will be back up as soon as Amazon (which is hosting the servers) fixes the bugs ! Nobody knows how long it might take.
More info about the OpenSSL bug here: http://arstechnica.com/security/2014/04/critical-crypto-bug-in-openssl-opens-two-thirds-of-the-web-to-eavesdropping/
If you want to be safe change your password on any OpenSSL based side as soon as possible !