Mealworms are real easy to sell. Just try here in the classifieds, or on ebay. Not sure which mail/package handler you should use but i think there are discussions somewhere on the kingsnake forums about that.
Deli cups with a little bran or what ever and small holes, put that in a small box with possibly slightly larger holes. Thats all you need to ship them.
An other option is to try to sell/trade them at the petstore. Not sure about Petco/Petsmart chain stores but any mom and pop shop would probably trade you for crix, but i don't know what the exchange would be.
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Later,
WhisQuila