It seems to me that you would want to pulverize your shells prior to introducing them into the garden. I don't think they'll break down very easily on their own.

Maybe you could let the kids (if you have invited any) whack the shells with a hammer.

Here is a link that might be useful: oyster shell

As is they could go in the garden path, it would be a Williamsburg garden. I'd crush 'em for the garden. If you are going to plant fruit trees next year the planting holes might be a good place for them w/ out the work of crushing them.

{{gwi:292005}}

I just bought some after reading they are a good snail and slug repellent. I think the critters are cut by the sharp edges. I'm going to encircle a plant or two and see what happens.
Ginny

I'd smash or crush them to bits and add them to the compost. In fact, I have a little stack of them next to my compost pile waiting to be smashed.

They'll release nutrients over time (especially calcium) and will improve the aeration of your pile and the tilth of the soil.