This is a great idea. I was thinking more for savory fillings like meat and or cheese, egg and bacon.
Turn your muffin pan upside down, bake cookie-dough over the top and voila, you have cookie bowls for fruit or ice-cream.
This is also good for insect bites or stings.
Freeze Aloe Vera in ice-cube trays for soothing sunburn relief.
Create a window-box veggie patch using guttering.
Use egg cartons to separate and store your Christmas decorations.