Just a heads up, Mojang had to shut down their servers due to an exploit found in SSL. This means you can't log in to multiplayer servers that authenticate through Mojang, which is almost all of them. They are working on it, but not sure how long it will take.

Article Link:
http://mcupdate.tumblr.com/post/8208...rvice-downtime

Notch's Twitter where he is giving updates:
https://twitter.com/notch