If you still have landline phone service and are looking for a cheaper alternative, Obihai is officially supported by Google again (it ended back in May 2014):
Obihai is excited to announce official support for Google Voice. With a Google Voice account and a companion OBi device you can make and receive VoIP calls on a regular telephone. To get started, just login to the OBiTALK website, add your OBi device and select Google Voice as your service. You’ll then confirm your account with Google, and within minutes, you will be making and receiving calls from the comfort and convenience of your home phone.
An Obihai VoIP phone adapter is a little box that will allow you to plug in any standard landline telephone and use Google Voice to make free phone calls within the US and Canada. You can also make cheap international calls starting at 1 cent a minute. Many people have been doing this happily since 2011.
To celebrate, Obihai is running a promotion where you can get a Obihai OBi200 VoIP Telephone Adapter from NewEgg for only $29.99 with free shipping (also works with Shoprunner) after using coupon code EMCPAWW99. Promo ends 9/14/14, or while supplies last. Retail price is $49.99.
Even though I am still quite happy with the quality of my Ooma VoIP phone service, it is really hard to beat 30 bucks upfront and no ongoing monthly fees or taxes. (Note: It is up to Google to continue offering free domestic calls, which they usually only promise a year at a time.) I just bought my first Obihai box just so I can tinker with it and maybe send it to my parents.