The duct tape of the kitchen
All kinds of useful
Some of the following uses may surprise you. Some may anger you. Others may just leave you thinking, "I knooooow, I totally use it that way every day." Either way, these aluminum foil tips and tricks may just save your life, so settle in, grab a beverage, and position your roll of aluminum foil so you can gaze at it lovingly while I extol its many virtues.
*To those of you who speak British English, the syllabication doesn't quite work here. Aluminum was given an extra i to make it sound like all of the other -ium elements: helium, plutonium, uranium, etc. This is equally correct; I'm just going to use the lazy American disemvowelled version. In the meantime, don't go getting any ideas about platinum. It'd sound weird with an extra i. Say it aloud, "Platinium." That's how aluminium sounds in the colonies. Rich and vibrant and just a little bit vowelly.
Step 1: Use it in the kitchen
Pie crust protector. Some aluminum foil folded over the crust of a pie will keep the crust from browning and blackening and eventually falling off before the rest of the pie has cooked sufficiently. This use: useful but not unusual. Its usefulness far outweighs its ordinariness.
Pressure cooker lifter. Placing and lifting bowls into and out of a pressure cooker can be dangerous. Hot food, hot bowls, and slippery surfaces make for a situation fraught with danger. Aluminum foil makes an excellent lifting apparatus to safely and securely raise the precious contents of your pressure cooker without scalding your hands, arms, counter, floor, or curious dog. Just use a piece of aluminum foil that's the size of your bowl plus about eight additional inches. You're making a sling of sorts to lift out the bowl with your newly-made aluminum handles. Fold the foil lengthwise two or three times for strength, then place your bowl into the cooker with your shiny improvised lifter. Fold the handles down during cooking, then use them to lift out your hot bit of deliciousness.
DIY cake pans. Oh no! It's your nephew's birthday and you were supposed to get him a cake shaped like Darth Vader wearing bunny ears. But you forgot because you were busy mayonnaising your hair. Don't panic! You can make yourself an awesome custom cake pan using aluminum foil and some creativity. Just use some aluminum foil inside another baking pan to create the outline of whatever cake you're trying to make. (This is great for county fairs when you want to make something in the shape of the county to woo city council into preferring your home-baked tribute to local government.)
Oven cleaner. You can protect your oven from thrills and spills by placing a few sections of aluminum foil beneath something that might bubble, bubble, toil, and trouble all over the floor of your oven. Don't foil the actual floor of the oven, as that could cause a build-up of heat to warp the bottom of your expensive appliance. Instead, lay some foil over the rack just beneath whatever it is that might erupt and create a mess. Instead of scrubbing until your elbows run out of grease, you can just ball up the soiled foil and recycle it. BONUS OVEN TIP: to protect your heating elements from the harsh chemicals in store-bought oven cleaner, put some aluminum foil over them before spraying down the interior of your oven. [EDIT] This may cause a potentially explosive chemical reaction, but your heating elements will appreciate your thoughtfulness while the house burns down.
Scrubber. I'm a big fan of cast iron frying pans. They're great, but clean up is sometimes a disaster. Using salt and paper towels works most of the time, but egg and rice (and the combination thereof after fried rice) tend to grip the pan like limpets. With a little bit of crumpled aluminum foil, I can scrub off tough messes. This works anywhere you might find yourself scrubbing unusually hard like post-casserole Pyrex, forgot-about-the-pasta-and-all-the-water-boiled-off pots, and caramel that's Maillarded to the point of crumbly blackness.
Campsite cooking utensils. The next time you're camping, you can lug around an entire kitchen set, or you can take a light roll of aluminum foil and fashion your own utensils and pans. You can make a frying pan using a forked stick with aluminum foil stretched over the crook. You can easily make plates and bowls, wrap veggies and meat, or even fold a spoon, fork, or spork out of aluminum foil.
Reheat crispy things. I enjoy the occasional pizza delivered to my door from a company whose name comes from a popular dotted-tile game. But I can't always finish the pizza in one sitting, and I need to reheat the delicious cheesiness. I'll microwave when I'm in a rush, but if I want ideal flavor I go to the oven with some aluminum foil. I set the slice directly on the foil and fold an edge over the crust to protect it from the heat. Bake at 350F for five or so minutes (or broil in high for two) and bam!: fresh-ish pizza. This method has the added advantage of instilling false olfactory hope in a roommate.