I’ve used COMC. It’s a neat website, but it’s a better option for buyers. You’ll have to ship your cards there and then pay a 25 cent processing fee per card. While your cards are for sale, you’ll be charged 1 cent per card per month for ‘storage.’ Then, if a card finally sells, you’ll pay a 5% commission. I wouldn’t bother sending a card to COMC unless it’s worth more than $1 because you’ll pay at least 50 cents in fees per card. In a nutshell, COMC is a great way to fill holes in your childhood collection, but not a great way to sell your childhood collection.