Blizzard has announced that beta opt-ins for the upcoming Cataclysm expansion to World of Warcraft have begun!
If you want a chance at partaking in the expansion's beta test you should head on over to your Battle.net account page and upload your system specifications as well as check off whichever of Blizzard's franchises (in this case Warcraft) beta programs you're interested in participating in.
Visit the official Cataclysm website for more information on the upcoming expansion.
[Thanks Chris for the tip off!]