This Google service allows you to get a US phone number that you can use to make calls, send SMS, use voicemail, etc.
Functions:
Sychronize it with your phone, tablet, and computer so that you'll always have your number available. You can get a transcription of your voice messages to read or send via email.
Activities:
Features include the ability to send messages to groups of people, block numbers, view your history, and create a backup of your activity.