If your computer has a "phone line" type modem, you can connect to a phone line and use your PC as a fax machine (you may need to install some software).
What might be a better solution is to sign up with someone like eFax, who do free accounts (though they do occasionally change your number and send you some "great offers" from time-to-time). You get a number to give out, which people then fax as normal. eFax then send you an email with the fax as an attachment.