Our phone company has a distinctive ring option that we use for our fax machine. Our monthly service comes with 3 free options (like caller id, call waiting, voice mail... and distinctive ring) We choose a distinctive ring as one of the options. As an extra it costs $3 or $5? per month. It gives you a seperate phone number that doubles on an existing line. When someone calls that number it rings twice. You can set up any fax machine to recognize the double ring and pick up only those calls. So we have 3 phone #s but only 2 lines. We have the double ring on our home line so that faxes don't tie up the business line.
I used WinFax for a while - has an answering machine feature. It works well, but almost overkill with all the extras.
My father inlaw got a fax service from the phone company. They provide a phone number, and anything that's faxed to that number gets sent to your email.