1. Tough Scrubber- a wadded up ball of foil actually makes a better scrubber than some of those scrunges that they sell specifically for that purpose. To clean baked-on gunk off of your lasagna pan or casserole dish, just go at it with a foil ball and some dishwashing fluid. I also use a nice big ball of foil to clean the greasy, burnt grossness off of my grill before and after use- it works just as well as the tools designed for the job, and you can just throw it away when you're done.
2. Spill Protector: Line the bottom of your oven in foil and it will save you from having to clean it of burnt-on food spills- in the event that something does bubble over (usually some kind of cheese in my house), just pull out the foil and replace it (wait until after your oven cools, genius). You can also like cookie sheets and pans in foil when baking, so you can spend your time eating the warm cookies, instead of washing dishes.
3. Paint Mask- If you're painting a wall or piece of furniture that has features you want to stay unpainted (doorknobs, drawer-pulls,etc), just wrap them in (you guessed it) foil! The foil is malleable enough to mold directly to the object and is easy to pull off once the job is done.
4. Impromptu Gadget- in a pinch, foil can be used to sub for other things around the kitchen- fashion a (double-layer) into a cone to use as a funnel or a piping bag. Use it to cover pie crust or roasted turkey in the oven to prevent it from burning before fully cooked.
5. Ironing Aid- if you need pressed clothes in a hurry, cover your ironing board with some aluminum foil. The heat from the iron will reflect back up, ironing both sides of the fabric at the same time. This works equally well when steaming clothes that can't be ironed.
Or, use it to fashion an awesome last-minute robot or knight Halloween costume. As far as what aluminum foil can do, these ideas are just the tip of the aluminum-covered cardboard sword. Er, iceberg.
photo credit: Real Simple