Email fax services let you send and receive faxes by email, or via the web. You don't need a fax machine. They provide you with your own dedicated fax number, so you won't need to tie up a phone line. Most of the free services are limited to sending outgoing faxes, with the ability to receive faxes limited to paying customers.
eFax gives you a private local or toll-free fax number in over 35 countries. You can send faxes via email, and incoming faxes are also sent to you by email so you never need a fax machine. You can try the service free for 30 days (send up to 30 fax pages and receive up to 130 pages).
FaxZero enables you to send faxes for free to anywhere in the U.S. and Canada. You send the fax directly from a form on the website, and can send PDFs, Microsoft Word files, graphic files and many other formats. FaxZero branding appears on the cover page for the free service, but you can pay to remove it, and to send faxes internationally.
FreeFaxtoEmail gives you a free UK-based fax number that you can use to receive faxes from anywhere in the world. Incoming faxes can be forwarded to your email address in PDF or TIFF format. Be aware that senders sending faxes to your number will be charged an additional per-minute fee on top of their normal connection fee (that's what pays for the fax service itself to be free). Outgoing faxes can be sent for a fee. You have to use the fax number allocated to you every 6 months or face losing it.
With GotFreeFax, you can send up to 2 free faxes a day to the U.S. or Canada. Each fax can be up to 3 pages long. The service supports a range of document formats, including PDF, Word, OpenDocument, rich text and JPEG. You can pay to send longer faxes, and to send faxes to other countries.
RingCentral offers a complete fax and phone solution, including a toll free or local phone number, the ability to send and receive faxes via email, voicemail (with free email delivery), call forwarding, on-hold music and more. You can try the service free for 30 days.