"We are happy to share that Google Voice is beginning to open up beyond former GrandCentral users. If you requested an invitation on the Google Voice site or previously on GrandCentral, keep your eye out for an invite email.

Once you receive your invitation, just click on the link and follow the instructions to setup your new Voice account. To help you find a Google number that is personalized to you, we've added a number picker that lets you search by area code and text. See if you can find a number that contains your name, a specific word or a number combination."

via http://googleblog.blogspot.com/2009/06/google-voice-invites-on-their-way.html