For years, my default solution has been to use FaxZero, a web site that lets you upload short PDF or DOC files to send to a fax number for free. You can only send 2 faxes per day, with a maximum of 3 pages each, for free. But you can pay to send additional and/or longer faxes.
Qipit is another web-based service that lets you send faxes. But instead of uploading PDF or Word documents, you can upload images you snap with either a cameraphone or a digital camera. Qipit will adjust the contrast to make sure they're readable and then either convert the documents into PDFs that you can email to contacts or allow you to send them to fax machines fo free.
You can only send 5 free faxes a week with Qipit. But if you don't need to send faxed documents very often, it's a whole lot cheaper than buying a Fax machine. Or a scanner.