Google is launching GrandCentral - that they purchased in 2007 for over $50 million - as Google Voice. The product is like Skype, a voice over IP service that offers free internet phone calls - "one phone number for all your phones for life" as GrandCentral noted.
The newly launched product will enable people to choose who's number gets forwarded to your cell phone or to voice mail. International calls will be for a small fee.
An interesting feature not offered by Skype is the ability to have your voicemail transcribed. The transcriptions can then be searched - a feature I am sure will get a lot of use.
Access to the new service should start soon - though apparently there are more than 15,000 people on the witing list as no new subscribers have been added since Google bought GrandCentral.