One of the big complaints you hear from those that learned on film is that, with digital cameras, people don’t take the time to make each picture count since storage is so plentiful. Perhaps there is a bit of truth to that but it’s just the way the digital world works. And there’s nothing wrong with that.
But for those that feel they would like to recreate that sense of being limited to just a few shots, it’s actually quite simple… Just scrounge up an old SD card, like 256MB or 512MB. If you shoot in raw, you’ll likely get 25 or 50 shots, respectively. With jpegs, you’ll get a 2-3x more. Oh and make sure that it is the only card you bring so you’re not tempted to add more.