I remember something about being able to recycle eggshells by crushing them
up and putting them to plants. can't remember exactly what for though -
something about nutrients. can anyone remind me again about it? does it
really help?

Fair source of calcium. Easy way outdoors, imho, is to
make a shallow trench between rows and toss in your eggshells, vegetable
scraps from the kitchen, etc, and cover with a little soil.
Continue until the trench is filled back in, then dig another.

Rinse the eggshells if you've got raccoons g

Kay