Google Voice is a free product/service that must be used.  It is perfect for businesses as well as personal use.  It is a product that is revolutionizing telecommunications.  PC World Just ranked Google Voice the #2 product of 2009.

The service provides a single phone number that rings all the lines you want.  Free text messaging.  It provides visual voicemail.  The service transcribes the message and displays it like an email. One can vary voicemail greetings by caller.  These are a few of the features. Here is more information on Google voice.

If you do not already have it, go get it. It is free https://www.google.com/voice