I use Myfax.com They give you a dedicated 888 number that people can fax to for about 100 bucks a year. It's really really easy. People fax stuff to that number and you get a PDF in your email inbox. Wanna fax something out? Easy. Just email your documents.
I have a mac and if you have a scanner and a printer, you also already have a free fax. I use a very inexpensive but nice USB Canon LIDE scanner, I think it was 50 bucks or so, it has three buttons on the front that, in concert with the bundled software, can be pre-set to act like a standard copy machine, a scanner, and a fax. The free bundled software from Apple and Canon includes a faxing program that sends and recieves, as well as an OCR program that will convert scans into text files for emailing or whatever.
The software can be configured to use a shared phone line with your dial-up internet, or it can sit on a voice line and wait several rings before picking up, in order to let voice calls go thru first. The software bundle includes drivers for PC versions of all this as well as a photo-stitching program and a paint/photoshop-like program. Pretty good deal for about fifty bucks!
On macs, the fax program is in one of the utilities folders, or just try a finder command to dig it up and activate it. With the Canon scanner and assignable buttons, it really is a one-touch thing, it prompts me for the number to send to, adds a cover sheet you pre-set if you want, and off it goes. For light duty occasional faxing, this may be all you ever need.
I hate the all-in one fax/print/copy/scan machines because if one part breaks down, you pretty much have lost everything else when it has to go get serviced. But that's me. They certainly save space. But they may compromise one feature you want most, like the quality of the scanning or the printing. The LIDE scanner and a Canon color i850 set me back under a hundred IIRC, and they have worked brilliantly for everything I need. The printer is very thrifty on ink, 12 dollar refills with the OEM Canon ink last a very long while, and pictures on the glossy photo paper are impressive. B&W text thruput is also fast, quiet, and thrifty. The faxing ability was icing on the cake.
I don't much use the fax here myself, before we had this functionality on the computer, we'd fax out of a nearby pharmacy that charged a buck for the service to send or recieve, or we used Kinkos. Again, a fair way to go if your needs are temporary or modest.