I also installed some extra packages, like mgetty-fax I think it was, and some others. I can print to a postscript file, then convert it to a fax-formatted TIFF using "fax make somefile.ps" and that creates somefile.ps.001, somefile.ps.002, and so on, one TIFF file/image per page. On my machine, the modem is /dev/ttyACM0 so on the command line, I can fax this to 555-1212 like so,
sudo efax -d /dev/ttyACM0 -h "MyFaxStation page %d of %d" -t 5551212 somefile.ps.*
And voila! Most of the time, it works (assuming I actually reach a fax machine on the other end, that is).
*EDIT* I forgot to mention, I bought a Zoom 3095 USB modem for this, excellent little device. It spends its life clinging tenaciously to the back of my PC like some long-forgotten barnacle on the underside of a ship. I forget it's there until I need it, which is the way I like it. (If you need some Zoom in your life, buy one. You won't regret it.)