Quick PayPal Order, which allows you to sell goods online, like PDF documents, ZIP archives, e-books, etc.
Easy configuration, where you set filename, price and your PayPal address. When a customer completes his/her order, they’ll receive an email with a unique download link to your product.
Very easy, automated & nice looking script, which should be very helpful for you. For more products, just duplicate order file, with different settings (price, filename)
UPDATED (2010/02/08): Additional verification added for processed orders and time limited orders, so customer – after he buy, can download product in defined amount of time (unlimited, 1 day, 2 days, etc)