Bleach them and air out.

Here in CA we put in water on the stove and cook out the smell....just barely bring to boil I believe.

http://goflorida.about.com/od/beaches/a/shells_cleaning.htm

http://community.cookinglight.com/archive/index.php/t-43833.html

http://www.usell-mart.com/seashells_faq.asp

http://www.scubaboard.com/forums/archive/index.php/t-56085.html

http://www.seashells.org/cleaning/liveseashells.htm

http://www.seashell-collector.com/Html/cleaning.htm

Wow! Thank you everyone!

My grandmother always put them in a bucket with bleach water in it over night. I still have some of her shells that she collected, oh my!, over 40 years ago! and they do not smell to this day. She rinsed them the next day and layed them out to dry. She and grandpa spent about 3 winters in FL before he died. When they came home, the shells got stored in coffee cans or whatever they had to put them in. They never smelled.

Tami

I read somewhere that if they still have chunks of critter in them to find an ant hill and let them clean it out.

Hopefully, I'm not hijacking by asking this, since it's not about shells..., but a few times I've purchased strings of crafting "pearls" and when you open the plastic bag, they stink just like a skunk!! I've aired, doused with Febreze, soaked in soapy water, etc etc but nothing would eliminate that awful odor, so finally chunked the pearls.:(
Any ideas, please?
Thank you!:)

Twinklenose, Put them in a plastic bag with some charcoal. Not the kind with the lighter fluid already in it, the plain stuff. Leave them sealed up for a few days. Worked when my car smelled like rotten milk, even after cleaning the carpet after the milk jug leaked. Also took the smell of spoiled food out of a refrigerator.

Tami