Here's a good list with a few options...
http://www.allfreelance.com/freelanc...-fax-services/

Forgot to mention, you can also use a Fax Modem...

Google a few of the following keywords for more info...
fax modem,fax modem software,fax modem driver,fax modem usb,fax modem mac,fax modem vista,fax modem freeware,fax modem for pc,fax modem switch,fax modem cards,fax modem and text for ip telephony...

Phil