I use Mal's E-Commerce
http://www.mals-e.com which is a remotely hosted cart solution. This means that you build your product pages on your site using static or dynamic HTML as you choose. When the buyer presses the Add to Cart button, they are taken to the remote shopping cart. This has a couple big advantages.
Number one is that it is very easy to create a good sound static html website that has a structure and naming that will result in good rankings with search engines. Most database shopping systems frankly stink (or other foul words) when it comes to search engine optimization unless you are prepared to put a lot of time or money into having the code rewritten or at least enhanced.
Number two is that the remote cart site is centrally controlled and administered by someone that knows what they are doing. Credit card security is vitally important and the server that hosts your cart needs to be designed well and kept up to date on all security fixes. Many web hosts don't seem to be interested/knowledgeable enough to do this unless you are paying big bucks to host. Most people here are no where near good enough to pull it off themselves. I don't even want to try to learn everything and take the responsibility and computer work with an emphasis in banking systems is my main career. There are people who make twice what I make responsible for security.
Mal's is a site that does it well and has passed all the required certifications for electronic storage of credit card information. It is also being re-certified constantly. If the cart is hosted on your domain, then you would be responsible for getting the certifications to be in compliance which run in the hundreds to thousands of dollars.
Cheers,