If someone asks you to fax him/her and you don’t have a fax machine, you can upload your file to faxzero.com and fax it to them! It’s free if it’s in the US or Canada and under 25 pages and you don’t mind having their name on the cover sheet; otherwise it’s $1.99 per fax (again, up to 25 pp.), payable via PayPal. (I don’t recommend PayPal, but here you have no choice, sadly). You can send international faxes, too. Those are $3.63 per fax, up to 15 pp. per fax. Disclaimer: I have not tried it myself.