If you're looking to sell your own products / services from your website, you're going to need a shopping-cart.
The shopping cart market is flooded with hundreds of different shopping carts you can choose from. But before you start on your journey, looking at product demos and interviewing vendors, it is important that you understand the two categories of shopping cart solutions:
1) An off-the-shelf shopping cart solution. Offers little customization but can be integrated with any website very quickly. Examples include: PayPal, MonsterCommerce, Yahoo Stores, InstantEStore and 1ShoppingCart to name a few.
These solutions are cheap, battle-tested and very scalable. Disadvantages are – very little customization options, limited support and you do not control the shopping experience.
2) Customized shopping cart based on a proven platform like XCart or OSCommerce. While typically more expensive to implement due to the time it takes to customize each platform, a customized shopping cart delivers full control to you as the merchant. You control the look and feel, shopping experience and any third-party plugins you wish to integrate.
Many large enterprises started with an off-the-shelf shopping cart and later switched to a customized shopping cart for a greater degree of control.
Disadvantages of going with a customized shopping cart are – Cost & time to implement (far more expensive), cost of maintenance, bugs introduced by your new code (it's not going to be as battle tested) and limited support.
Since the platform people (XCart, OSCommerce etc) are in the business of developing their platform and not selling shopping carts, you typically get a third-party vendor to handle the customization.
Recommendations for picking a quality shopping cart:
1. Ask for references in the form of live websites using the shopping cart. Go to these websites and try to buy something as if you were a customer. Write down notes about your experience. Likes and dislikes.
2. Check the page.
3. Find out who are some of the largest merchants using the shopping cart and what is their volume. Make sure the shopping cart can scale to meet your needs.
4. Customer Support – Your shopping cart will become integral to your business. Send an email to the company's general support @ box and leave a vmail at the technical support box. Measure how long it takes to get a detailed (non canned) response.
5. Open architecture – If your needs change you might decide to switch to a different shopping cart in the future. Make sure the cart you're picking now offers full export of the entire database of customers, orders, products, etc. to make a possible future switch pain free.