Google Voice has the option of forwarding all incoming calls to multiple numbers.  Additionally, it can forward calls to a Gizmo number.  Gizmo, is a standard SIP-based VoIP service.  Meaning that an Analog Telephone Adapter can be used to attach any standard PTSN telephone you want to your Gizmo account.

So what does that really mean?

After registering for a Gizmo account, I set up my ATA, similar to this $30 ATA from Grandstream, to use the Gizmo service.

Then I configured Google Voice to forward calls to my Gizmo number, which requires an exciting verification process that consists of answering the phone and dialing 2 numbers.

Voila!  Free incoming calls to a real phone at my house, which has no standard pots landline.  Additionally, if I get bored of talking to you on my landline, I just press *, answer on my cell phone and hit the road.