This site provides the facility to send and receive faxes to any US numbers for free. The main thing is that it does not need any email registration and it is 100% free. To send a file, upload it and enter the fax number and send it. To receive create a cover letter send it to whom you want to send the fax, that will reach your drop.

Check the site that also contains some other free facilities also.

For fax : http://drop.io/fax

The website : http://drop.io