In case you missed the email from Google, here's the transcript of the message I got.
Dear GrandCentral User (withheld):
We're writing to let you know that we will be closing down the GrandCentral website as of December 31, 2009.
All GrandCentral accounts were upgraded to Google Voice earlier this year, but since that time, you've still been able to log-in to your GrandCentral account and listen to old messages there. You will no longer be able to log-in to your GrandCentral account after December 31. Because of this, we strongly suggest downloading any messages or contacts that you want to keep in the next 43 days.
We will send you another reminder before closing down the site, but we suggest you take action now to download any information you want to keep.
- The Google Voice Team
You've received this mandatory service announcement email to update you about important changes to your GrandCentral account.
Google Inc. - 1600 Amphitheatre Parkway, Mountain View, CA 94043