eFax.com

Advantages: Free, enables anyone to have a fax number, even without a machine
Disadvantages: Voicemail service is poor, but who cares?

eFax.com is a website that will provide you with a free fax number, which can also be used for voicemail if you so desire. You can also upgrade to a paid service which offers more features. You are given an 0870 (national rate) number. When someone sends a fax to this number the eFax system converts it to a file in their own .efx format and sends it to you as an email attachment. You then open it using the free software they provide you with. It ...
...like a normal fax. The voicemail is less useful, because callers are only allowed a short message, and they hear a tedious 'eFax' advert in an irritating American accent. All in all, the fax service is extremely useful and easy to use - if you combine it with some fax software so you can *send* faxes as well, you're well away! The voicemail service however isn't worthwhile. ... Read review

Advantages: Sometimes works
Disadvantages: Not reliable and very expensive, appaling customer service

...UK operation was sold to Efax.com in the States earlier this year and service is now awful. Calls to the 0870 number are often unobtainable, if you use the service to send a fax from their website the calls that cost a few pence now cost a £1 a minute as they are sent from the US at international rates (and then some). The "customer services department" acknowledge email but never reply. They also have a service that provides an ansaphone to email ... Read review