For digital or downloadable product selling, it is hard to find a Free service. Paypal and other services already takes their commissions. If you wanna sell cheap products, you cannot get even 10% of your real price. I started to work with theContentBazaar com . It is not advertising, I believe that if they will get more sellers, the marketplace will be more crowd. They have very good distribution channels. Just take a look and compare it with other services. You will thank me :)