Eggs need to be used as fresh as possible only if they are not really cooked (or if there is a pregnant woman around :). Otherwise they’ll stay good very long, much longer than the use by date (which on most products is nonsense anyway).
If you’re unsure, break them in a separate bowl. If they don’t smell bad (and don’t have feathers ;), they are good to eat.
Once they are really bad, there is little you can do with them, except bad jokes :)

Be sure to keep the shells for use in your garden. Full details here.

Yeah, just throw them at people, if you’re feeling mean :-D

I’ve read that hard-boiled eggs will peel easier if the eggs are older. I always hard-boil mine for lunches, snacks and salads if I’ve still had them for 2 weeks.

legally, eggs in the supermarket can be up to two years old if refrigerated properly. (It’s awesome having my own laying hens).

My grandma had a chook house and to test the eggs for freshness you can place them in a sink or bowl of cold water. If they float at all chuck them. If the stay on the bottom they are fine to use in cooking.

you can poke a hole in both ends with a needle and drain out the egg, then fill the egg shell with paint using a syringe and use it for modifying billboards and fur coats…

Most of my ideas have already been suggested, but you can blow the liquids out, wash the inner shell, open the bottom a bit, put in small trinkets and then plug the hole with paper.

Put a tag on it that says “smash me” and hand it to a friend.

You can make holes in the top and the bottom to get all the liquid out, wash and dry them, then make a little loop from a bit of wire, separate the ends & insert them in the hole from one side (you can later put the ribbon through this hole and hang your craft on a x-mas tree or something else..)You can then paint the eggshell with your favorite designs, and use it to decorate your room or garden. They are good for kids crafts too - you can glue hats to them and other bits made from paper.
One woman makes real art from them: http://www.annseggcraft.co.uk/ - if you feeling brave, you can try it too.

You can also make eggshell mosaics!

You can make them into Mexican Cascarones:
http://www.associatedcontent.com/article/558645/how_to_make_mexican_cascarones_confetti.html

I kept old eggs someone had left in my fridge. I used one the other night by throwing it on a car honking in my street at midnight…the quiet came back right after that!

otherwise I use the white to varnish stones to give them a wet look or on wood to give it a honey look. (no smell).

http://vertes-et-mures.blogspot.com/2008/03/rutiliser-recycler-des-vieux-oeufs.html