I'd like to be able to setup faxing by running a virtual fax modem. I don't understand how fax messages are sent and received, and I don't know much about COM, or how the fax modem communicates with a fax service. I've read forums out there, but I haven't found a very good explanation on this topic, nor a good tutorial on how to set it up with open source products. If anyone knows of something that's cheap to buy but works excellently, then by all means, let me know. Also, will I need to purchase a dedicated phone number (land line) for setting this up? I want to be able to receive and send faxes. I might be on the wrong track here, because I wasn't sure if faxes could be received virtually either. That's another question I had. If this post is horrible and should be split out into separate questions, let me know and I will do so. I'm open to running things in Linux or Windows. I will vote up for any feedback what so ever. The first thing that works well I will mark as the answer. Trust me, if you give me some good feedback, it shouldn't take me long.
SnapOverflow
You're looking for HylaFAX. It uses a getty-alike to receive faxes and email them appropriately, and either a CLI tool or a virtual printer to send them.
Also look into Esker VSIfax. It's commercial, but is a fully featured automated fax suite. It runs on Windows and Unix variants, with the ability to submit jobs to virtual fax servers.