Use your smartphone to scan objects you want to print.
The most accessible way to generate your own models of real-world objects is through, you guessed it, an app for a smartphone or tablet. They won't remotely approach what you'd get from a dedicated 3D scanner like the Digitizer, and as we've discovered in our experiments, they offer extremely erratic results. However, as with all things 3D, the fun is in experimenting. (And since they're free or cheap, these apps are worth fiddling with if you don't want to shell out for a dedicated scanner). Our best results came from 123D Catch by Autodesk, but our models still required some cleanup and retouching, which might put off less patient types.