E-commerce (selling products online) can be complex, so don't be satisfied with my basic recommendations below. The order of selecting the pieces is as follows:
If you reverse the order of these selections because of impatience or some slick salesman, you may not get the optimal shopping cart for your needs.
PayPal. PayPal can be the simplest shopping cart, a payment gateway, and a merchant account that allows you to take credit cards. Check out the tools for merchants, especially if you're trying to set up on a shoestring. PayPal is quite cost effective until you get above about $1,500 per month in revenue. But it is harder to automate as fully as stand-alone shopping cart systems with their own payment gateways.
1ShoppingCart. 1ShoppingCart wraps into a single piece of software several powerful applications: a shopping cart with digital delivery, a listserver for newsletters, an autoresponder, an ad tracker, and an affiliate program. It's best if you have only a few downloadable products. If you're selling more than a handful of tangible products, don't get this. What you'll need in addition is a payment gateway (such as Authorize.net) and a merchant credit card account.
I'm going to resist the temptation to recommend other shopping carts. A lot depends on what you are selling and how customized the sales process must be. Some of the most popular carts for small businesses are ShopSite (I use the Pro version), Miva, Magenta, etc.
What will you sell in your online store or on eBay? There are two main approaches. (1) Purchase product for about 40% to 50% off retail and keep it in inventory until you sell it. (2) Contract with drop-ship companies at about 30% off retail to ship the product to your customer when you send them an order, and then they bill you for the costs. The latter means much less money tied up in inventory, but it's harder to provide excellent customer service.
Drop Ship Source Directory from World Wide Brands is, in my opinion, hands down the best and most up-to-date directory of products to sell online. You purchase a non-expiring subscription to view the catalog online. It contains about 2 million brand name products, with information on how to contact the suppliers -- all updated and researched constantly.
If you sell very much, you'll need order management software to handle the complexities of fulfilling, drop-shipping, returns, cancellations, split orders, etc.
is the best I've seen for small to medium companies. It is desktop software written in MS Access. It contains modules that allow it to interface with one or more of the following e-commerce platforms: AbleCommerce, Amazon.com Marketplace, Americart, Global WebCart, Half.com by eBay, Miva Merchant, MonsterCommerce, osCommerce, Seller's Assistant for eBay, Shop.com, ShopSite, and Yahoo! Merchant Solutions. It isn't inexpensive, but is powerful if your sales are starting to ramp up.