I use Boxshotking to create book cover graphics, banners, and ebook covers. It is easy to use and it is my favorite graphics program. It is easy learn and implementation is quick ... and everything happens online. I love it. (Disclosure: affiliate links appear in the PDF. I receive some compensation when you purchase the program using this link.)

1. Video Demo
Watch this video to see how quickly you can create product graphics for your site:

2. Quick Start:
Creating Your First Boxshot