If you have a Battle.net account and opted in to take part in a possible Diablo 3 beta. Then you need to check your fucking email right now! Blizzard has started sending out beta invites for Diablo 3 and is playable right now to anyone who has one.
If you didn't get one, don't worry, Blizzard will be giving opportunities like contests or give aways, so I suggest start following them on Twitter ASAP. They also warn anyone still looking to get a beta invite to NOT click any links and go directly to your Battle.net account to see if you got in.