Shopify is a hosted ecommerce solution with integrated payments. People who sell stuff online, or want to, are going to like it. You can set up a store in moments, add items to sell, upload images, add tags and group items, and integrate paypal or a credit card processor for payments. Reporting is excellent, and they’ve even thought to include a RSS feed of recent orders to keep track of sales.
See here for more details on features. In general, sellers will be able to create a very professional multi-page website with little or no programming skills in just a few minutes.
There are a number of pre-made themes for the shop, and themes can be modified by directly manipulating the CSS. Shopify has also released a product called Vision, which is a downloadable client application for designers to build and modify their own shopify shop themes.
Creating a store is free. Shopify takes a 3.75% commission on all sales.
So Shopify will help you set up a very nice store at a reasonable price. But they should quickly build tools to help people promote these stores as well (Vendio, for example, has some basic promotional tools, and they also assist with ebay listings). If shopify can help store owners with marketing, too, it’ll become a more useful service.