Blizzcon last year? Well, Blizzard is now accepting them. All you have to do is head over to this website, enter the appropriate info and you should receive an email confirming your "Blizzard Future Beta Sign-Up."
Alas, the email doesn't mention what the beta will actually be for, nor does it say when the beta will occur. If we had to guess -- and we do -- it's probably for StarCraft II or Diablo III, both of which have betas planned. StarCraft 2 seems the likelier choice, given that plans for a 2009 beta were revealed earlier this year.