Recycling . . . I love using something that is usually thrown away in useful ways. Eggshells are free and so beneficial in the garden.
As long as I can remember, eggshells were always put in the soil mixture when first planting tomato plants. We sprinkle eggshells as a mulch when slugs become a problem. Those are the ways we have used eggshells in our organic garden.
I never used an elaborate technique for preparing the eggshells . . . just dried them out before using them. However, I have since learned it is important to prepare them for use in the garden. Here is an excellent article on how to prepare your eggshells before using them.
11 Ingenious Uses for Eggshells from Good Housekeeping
Other links with information on using eggshells in the garden . . . from eHow and How Stuff Works.