The idea is to use a thermal printer rather than film. While the print quality is pretty horrendous, the prints are dirt cheap. I mean, fractions of a cent per print.
Problem is, you can't buy a PrintSnap. At least not yet.
Then along comes ProgrammingPraxis, with an essay about setting up a Raspberry Pi security camera. The setup essentially involves configuring standard Linux tools to capture images from a Pi and ship them off over e-mail.
Whoa, if a Raspberry Pi can trivially grab photos, then can it also print to a thermal printer? Apparently so. Here's a few tutorials that show this is done: Little Box of Geek, Raspberry Pi Thermal Printer One-Time-Pad, Internet of Things Printer for Raspberry Pi.
Looks like this is totally doable. Heck, the Little Box of Geek even gives a detailed parts list. OK looks like this is going on the project TODO list.
Oh, and one last thought: maybe I'm over-thinking this. What if I could just print my photos from my cell phone? It's pricey, but this thermal printer claims to do just that. And eBay has a number of Bluetooh Receipt Printers that look like they may do the job. Nahhh, what's the fun in that.
Update: and here's two more useful links: SparkFun Thermal Printer, An open source kit for exploring the possibilities of internet-of-things printing.