So you're not convinced by The Impossible Project's $3-a-shot reimagined Polaroid film, and the rising cost of increasingly scarce original cartridges is making you consider retiring your camera; how about modifying your Polaroid shooter for use with regular sheet film? It's not a process for everyone - the camera probably won't ever use Polaroid film again, and you won't get your prints instantly - but if you love the optics on your Polaroid Spectra then this Instructable is for you.
The Spectra is known for taking better quality photos than the Polaroid-using rank and file, and the Instructable goes through fitting an AA battery pack, modifying the exposure system to allow more light through, and then tweaking the cartridge slot to suit regular sheet film. You'll also need to craft a film holder to fit the camera (and learn to ignore the odd grinding noises the Spectra makes when you load it in).
As for the end result, it looks pretty impressive - though obviously you'll have to do the developing yourself. A pack of Impossible Project film - when they've tweaked it for better picture quality - is always going to be easier, but if you're a photographer on a budget then this could save some serious money while letting you still enjoy your favorite camera.