What is there to feel unsafe about? You advertise. Someone buys. You make sure their check clears before shipping the merchandise.
You buy something, you send a money order so your personal checking account information is not available to the seller. You have their address (needed in order to send your payment). If they default, you notify Craigs list and the authorities of potential fraud.
It is no different than buying any item on line, or posting your stuff of Ebay.
If the item you buy is too big to ship, you go to pick it up with a friend.
If the item you sell is too big to ship, you make sure there is someone at home with you when they come to pick it up.
Or use FedEx or UPS to ship.