I’ve found a few fax sites that will allow incoming faxes for free or cheap, but for outgoing they want you to subscribe to a monthly service. I only fax a few things a year. Currently I have to go into town to a quickie mart and pay $1 a page. I’d gladly pay $2-3 a page online, but can’t justify a subscription.
I believe it’s free with Windows XP.
Don’t know why I didn’t think of this first: if you have a modem grab any of many freeware/shareware software programs available and use your computer as a fax machine. Be sure to test it.