While there are dozens of web-based services that let you send and receive faxes from the computer without requiring a fax machine, Interfax goes one step further – it turns your Google Docs into a complete fax machine.

You just have to connect your Google Docs account with Interfax and once the link is enabled, you can fax any of your existing Google Docs documents, or spreadsheets, to any fax number in the world right from the browser. You may even send the same Google Docs file to multiple fax machines in one go – remember to separate the different fax numbers / Google Contact names by commas.

The cost for sending faxes from Google Docs varies according to the destination country and the length of the document. For instance, if you are to send a fax to US, the cost would be 13 ¢ per page, 15 ¢ for UK while a single page fax to an Indian number would cost you 60 ¢. There’s no monthly fee for sending faxes though you’ll have to buy minimum credits for $10.

GinzaFax is another online fax service that is built around Google Docs. It is slightly more expensive to send faxes through GinzaFax – the cost 40 ¢ per page for US numbers and 60 ¢ for other countries – but here you get a $5 free credit for sending faxes the first time you sign up for an account.

Other than sending faxes, you may also use both Interfax and Ginza Fax to receive faxes from anywhere in the world directly into your Google Docs account. The incoming faxes are automatically converted to PDF format and they get saved in a separate folder thus making it easier for you to locate them later.

Also see: Choosing an Internet Based Fax Service