One of my tasks to-do is to incorporate a shopping cart, so the visitors could by my photographs. Such endevour requires a merchant function enabling the visitors use credit cards. Currently I am looking closely on PayPal services. One of which is the Shopping Cart. PayPal is widely used and trusted; and visitors would not need to provide their credit card information as it is stated in PayPal's The e-Commerce Safety Guide:
"When purchasing something using PayPal, users simply carry out the transaction through their PayPal accounts, rather than a credit card. PayPal then charges each purchase to the individual’s credit card or checking account. Because all PayPal transactions are based on the user’s e-mail address, merchants never have access to the user’s account information. This method is safer, more secure and more convenient than providing financial information to multiple sites of individual sellers."
This guide provides a lot of information on online fraud, identity theft and similar topics.