I have written several times about Google Voice, a great service that provides free phone calls to North American numbers and also combines all your telephones (home, office, cellular, etc.) into one phone number. You can read my past articles at http://goo.gl/maRqF. Starting today, Google Voice now offers number porting: you can transfer an existing telephone number to Google Voice for a $20 fee. Now you can use all of Google Voice’s features without having to give up your long-time phone numbers.
There are quite a few restrictions, similar to the restrictions on porting numbers to cell phones. You can read the details at http://googleblog.blogspot.com/2011/01/port-your-existing-mobile-number-to.html