Someone else just posted about Google checkout, which works very similar to PayPal. You do need to set up a Google account. The biggest problem would be that it is so much more likely that a customer will have PayPal rather than Google.
PayPal has been by far the fastest way for me to purchase items. Because the seller has payment almost instantly, I don't have to wait before the item is shipped. As a seller I would find it more difficult to keep track of payments and shipments if accepting money orders and checks, plus for checks I would really want to have the check clear before sending the package.