Google Voice now has a free service that can give you a free local phone number that can receive and make calls, SMS texts and voicemails.
Incoming calls are free, and calls to the USA or Canada are free.
Receive the calls online via Google Voice service.
You can receive the calls via Google Voice online, same as using a normal phone. As well as have voicemail, and SMS texting.
Use the voicemail service only.
You can use the service for voicemail only, and receive notifications of new messages. Which you can listen to online, or over the phone if you call your Google Voice number, and press * when you hear the voicemail greeting.
Forward your Google Voice number to another phone. Such as a mobile device.
You can forward your number to a mobile device or other phone. You have options of asking the caller for their name, showing their caller ID on your other phone when receiving, and having text messages forwarded as well (Text messages forwarded are sent from a special number, when you reply, they show the sender as your Google Voice number.).
Making calls online via Google Voice service.
You can make phone calls from the interwebs via Google Voice service.
Making calls on a phone via Google Voice service.
Call your Google Voice number, press * when presented with the voicemail greeting (You will be asked for pin instantly if you have enabled forwarding to the phone you are calling from). Press 2 in the menu to make phone calls free from the service. (The caller ID of the receiving number will show your Google Voice number.)
These of course are not all the features available. But a brief summary.
Sign up for Google Voice.http://www.google.com/voice