Egg Shells

Treat Skin Irritations
Dissolve an eggshell in a small jar of apple cider vinegar (takes about two days) and use the mixture to treat minor skin irritations and itchy skin.

Tonic
Powder the eggshell to a fine powder and take 1/4 tea spoon a day for 400 mgs of calcium.Oh and don’t forget you need to add some lemon juice to the mixture.

Eco-friendly Household Abrasive
Shake crushed eggshells and a little soapy water to scour hard-to-clean items like thermoses and vases. Crushed eggshells can also be used as a nontoxic abrasive on pots and pans.

Grow Moss on your plant pots and stuff
 Mix existing moss with powdered milk and egg shells, grind it all up and paint it wherever you want the moss to take hold. Apparently moss loves calcium so the egg shells and milk activate it.

Feed Your Plants
Dry the egg shells, grind them to powder and store in tins or jars.
When planting calcium loving plants, add some of your egg shell powder to the hole around the roots.

Kind thanks to RecycleThis.co.uk and their commenter's for the tips above

How to Make Eggshell Sidewalk Chalk
This chalk is for drawing on sidewalks only, not for chalkboards.
You will need:

• The shells of 6 eggs
• 1 tsp very hot water from the tap
• 1 tsp flour

Wash the eggshells well, so they don't have any egg left in them. Dry them and grind them with a rock on the sidewalk or other concrete surface. Make sure the rock you're using for grinding is clean so you don't get dirt ground in with the eggshells. Grind the eggshells into a fine powder. You'll need one soup spoonful of this powder to make a stick of chalk. When you have enough powder to make a stick of chalk, sift or pick out any little bits of eggshell that are still not ground up and throw them away. Scoop the powder into a cup or paper towel and bring it into the house for the next part.
Stir the flour and hot water together in a small dish to make a paste. Put the soupspoonful of eggshell powder into the paste and mix well. It may help to mash it with the back of the spoon. Add a few drops of food colouring if you want coloured chalk.
Shape this mixture into a chalk stick. Then roll it up in a strip of paper towel and set aside to dry. (Drying takes about three days.) Then just peel the paper off one end and you're ready for some sidewalk art.
For really big sticks of chalk, try making 3 times this recipe, and stuff the mixture into an old toilet paper tube. When it's dry, you can peel away the cardboard as you use it

Thanks to MakeStuff.com for this one