If you want a site that sells digital goods (such as eBooks, software, or music), you can use a full-feature cart like ZenCart, X-Cart, or CubeCart that accommodates digital downloads.

Or you can use services such as e-junkie.com, Payloadz.com, StreamingDelivery.com, and others listed here. The first two listed happens to be recommended by Damon, PayPal Developer Community Manager [reference source].