Hellofax is a well known online virtual faxing service and they have now integrated with Google Drive. This integration means you can fax any document from Google Drive (and Google Docs) and even receive faxes directly into a special Google Drive folder.
In addition to the faxing, they also offer the ability to edit and virtually sign documents (eliminating the need to print, complete, scan then fax).
They have a promotion where you get 50 free fax pages per month and unlimited signature request and document signing as long as you sign up for the service using your Google Drive enable Google Account. So make sure you have Google drive then sign up using this link.