One way to bedazzle kids about the utility of science, and to teach about solar energy, is to make a solar cooker for them using household items. This is a great science project for a science fair and makes a solar cooker out of things you can usually find around the home. It's also something you can make and bring with the family on a camping or fishing trip, and should inspire a lot of creative thinking.
Paint the box (or cover the box) with black construction paper or paint. If you have some reasonably dark fabric, you can coat the box with that as well. Explain to your kids that the black paint means the box absorbs more energy than if it was colored white or some other color.
Cut a rectangular flap out of the top of the box lid, so that there are three cuts--two short ones parallel to the short ends of the box and one long one parallel to the long edge of the box. Put a small crease in it so that the flap sticks up.
Glue aluminum foil to the inside of the shoe box; you're making a reflector, so make the shiny side the one that faces out. Glue aluminum foil to the inside of the flap you made in the lid as well.
On the inside of the box lid, lay a sheet or two of Saran wrap, or clear plastic and glue it in. This will trap the heat inside the box.
Put your cookable items (hot dogs work well for this) inside the box, and put the lid on. Prop the flap up so that it reflects sunlight into the hole in the box top, and set it out on a spot where the sun shines. If you're out camping, don't leave it unattended--you're likely to attract animals who'll find the box an interesting challenge to open with a tasty reward. Depending on the brightness of the day and the quantity of food you're cooking, it may take anywhere from 20 minutes to two or three hours to cook something.