Google Voice is FREE for making and receiving calls in the lower 48 states... not sure about those other guys (Alaska & Hawaii)
When you join, You pick out a phone number. You pick what phone rings when someone calls it..
You can have it ring your Cell Number, Work Number or Home Number.. Or have it ring all (3) at once!! If you don't answer you are sent to their version of Voice Mail.
This is were the fun and usefulness starts.. When someone leaves me a Voice Mail, A TXT message is sent to me phone with the callers Name (if there in my Google contacts) and number, PLUS the Voice Mail is transcribed into TXT... (not real accurate yet but getting better all the time)..
Yea you can even call in and listen to your Voice Mail just like you do with Verizon too.. You can also go online
www.Google.com/voice and manage you Voice Mails and SMS Messages... You can replay them, even DOWNLOAD your Voice Mails in .mp3 format... You can keep them as long as you want or delete them as desired..
There are tooo many features to describe here.. You can divide you contacts into groups and each group will hear a different greeting (that you recorded)..
i.e A Business Caller will hear your Business Greeting
A Family Member hears the recording you made for Family...
It's endless.... You can even have recorded greetings for individual callers...
You know that personal little touch for the one you love..

Well Check it out... It's current invite only, but you can request one on the log in page...
I may be able to dig up a few instant invites toooooo