Google really took their time on this one, leaving GrandCentral sitting dormant ever since they purchased it in 2007. But nonetheless, it's back, and now it's called—wait for it— Google Voice.
For those of you who haven't heard of it, GrandCentral/Google Voice is an online phone consolidation service. Basically, you pick a single phone number for your account, and have Google Voice—which can manage calls, voicemail and now SMS—route contact to that number to any number of other phones. It's sort of like a web-based switchboard for all your devices.
Google has preserved GrandCentral's functionality, and added a few features to their web client. For example, now you can see your voicemails collected on your PC and transcribed, or have a voicemail transcription sent to your phones via SMS. Speaking of SMS support, that gaping hole that blighted the old GrandCentral, it is now included and logged accordingly. Conference calling and cheap international rates are also available through the client.
Google Voice is in beta, but it's one of those trademark soft, open, indefinite Googly betas. It's closed to everyone except previous GrandCentral users, and the company says that the beta will open to the rest of us "soon". [Google]