The online sensation being GrandCentral.com is finally closing down for good on December 31. 2009, as you might know GC was purchased by Google and turned into Google Voice a while ago.
The service offers everybody in North America a free phone number with voice mail, you can then configure the one number to ring up to 5 of your other telephones when called, Google Voice is going to offer the same functionality but closely integrated with other Google services, right now GV is only available by invitation, but I figure that is going to change once GC closes down at the end of the year.
http://www.grandcentral.com/
http://www.google.com/voice/
