A now Google owned service called Grand Central has been opened up to beta in the US. It's a "one phone number" service, that directs people who call you on say, your home or work number, to just one number. It can also blacklist numbers and other stuff.
I'm unfortunately in the UK, so I can't try it out
Any US forum members trying it? Or fancy trying it and giving us some feedback?
The address is
GrandCentral: The New Way to Use Your Phones