As a professional art director in the interactive advertising space, I struggled with this question for a while. My first site was a straight HTML site, utilizing the shopping cart within the PayPal umbrella. I quickly realized that this was quite annoying for my customers. The PayPal shopping cart opens in a new window in the browser, and was confusing some visitors.
After an exhaustive amount of research, installing OSCommerce, eBay ProStores, ZenCart, Magento, and Joomla (a CMS with PayPal integration), I decided to build it myself, with a little help. If you are familiar with Adobe Dreamweaver, and have a light knowledge of PHP, you can get a plugin that is an eCommerce engine. It's called eCart, from WebAssist. It's a little pricey for a beginner, but it's not outrageous. It allowed me to build the site I wanted, while not having to worry about the shopping cart, checkout pages and a direct tie-in to PayPal.
I have now rebuilt the site for the third or fourth time from scratch (I tend to do this every six months or so). I redesign it because that's my profession, and as the site's number one visitor, I get tired of the look and feel. The site just relaunched about a month ago, and I am already tired of it. It's too simple, and lacks the brand feel that I have tried so hard to build. But, that's my full-time job speaking.
Here's a link to the WebAssist tool. WebAssist eCart Dreamweaver Extension