For starters you can ssprinkle the shells around your garden to help keep pests out like like slugs or snails, they don't like crawling over the sharp pieces of shell. I also toss some of them into my compost bin.Use them to start seedlings, they are great for that and for the plant its self. Plus you dont have all those trays left over when your done. Don't forget to use your egg carton to hold them.
Oh and first aid treatment- Fresh egg membranes applied, then allowed to dry, will “draw” minor infections: splinter, pimple, boil, etc. I know sounds funny but it works.
Crushed egg shells work great to scrub pans that have food stuck in them. Yes they will break up, but they still do the job and when you have nothing at that moment cause you forgot to bring something with you camping per say...then this is great.
This is one that I have read but have yet to try it. Make it into a powder and add a little bit to your nail polish to strengthen nails. Take that same powder and put it into ice cube trays with water and rub it on your face– it helps reduce the look of wrinkles. Put the powder in your lotion– it softens your hands. Doesn't sound like it could hurt anything.
House Plant Booster, My Grandmother Domaslay kept eggshells covered with water in a mason jar and she used to water her plants with it.
I would like to add one more thing... you will do better to use your own eggs or lets say not store bought as often as possible. The eggs are week in everything and who knows if they are caring bad germs. Not sure if I said that right, but I think you can get what I'm saying. Buy from your local small farmer to help you and them. Free range eggs are only free if they are not pinned up.
I hope this short incite gives you some ideas. Send me some of yours and I will gladly share them with everyone.
Have a sun shinny day.