I had to send a fax yesterday and search turned up faxzero
I see it has been mentioned a couple of times over the years on DC. Last mention I found was May this year. Just thought I'd note it does still work. The one stumbling block for someone with a Laptop and no phone is it will not send a fax unless you enter a valid phone number.
It does allow adding up to 3 pages. Not bad for a free service. I have no scanner but I used my Laptop webcam to take snapshots and convert the jpgs to pdf for faxing.