Or I should say, what to do with one of those old 35mm film canisters. Turn it into a DIY diffuser for your DSLR's pop-up flash. Those little built-in flash units are convenient, but tend to produce fairly harsh light and very deep shadows especially when shooting closeups of people indoors. A diffuser can soften the effect. Contrary to what you might think, diffusers don't actually filter light to make it softer. What they actually do is increase the physical size of your light source by spreading the light from your flash, which is smaller, and thereby scattering (i.e., diffusing) the light more.
You could always buy a relatively inexpensive commercial diffuser, like this one or this one, but making one yourself can be just as effective and free (not to mention the instant gratification). Professionals and enthusiasts have used all sorts of white, translucent objects as ad hoc diffusers: ping pong balls, pieces of milk jugs, white Post-It notes, and even tissues. But my favorite idea is the white film canister (like the kind you used to get your Fujifilm rolls in). It's easy to make, sturdy, pocketable, and better yet, recycled. You can probably figure it out yourself, but here's a step-by-step how-to with photos. Of course most of us no longer have a steady supply of film canisters. I used to be awash in them living with a professional photographer, but now they're a rare and valuable commodity in our house. Luckily, there are enough Luddites out there frequenting the one-hour photo counter at your local drug store that you can just stop by and ask them for a couple and they're usually happy to hand them over. And you can feel good about keeping one more plastic object away from the garbage continent.