The Diablo 3 beta has been running for quite some time, however last weekend Blizzard sent out 275000 more invites as part of a stress test in the lead up to the final release on May 15.
If you were one of the people lucky enough to get a beta invite, then enjoy it while it lasts, as the beta will close on May 1. At that time the beta servers will be brought offline, and posting rights on the Diablo 3 forums will be restricted to those who pre-purchased the game, or who have active Starcraft II or World of Warcraft licenses.
You can expect a full preview of Diablo 3 based on the beta later this week here on Rocket Chainsaw.
I am so glad I was able to finally get a Diablo 3 beta key! I wish I could play it longer though as May 1st is approaching quickly. But if anyone else is still in the hunt for a beta key you can try this website (this is where I got my key) http://www.deviousdog.com/diablo3betakeygiveaway/