I used to receive several junk faxes, daily.

At the risk of receiving even more junk faxes, I elected to call the 800 number at the bottom of the junk faxes to have my fax number removed. For the most part, it's an automated deal requiring you to punch in your fax number.

I'm pleased to report that this actually worked, and drastically cut down on the number of junk faxes I receive. Occasionally, I'll still receive the rare junk fax (perhaps once or twice per month, at most), but certainly nothing like before.

This method also worked well for my neighbor in the office next door.

It's a bit of a PITA, but well worth the minimal time and effort involved, and the results obtained, imo.