The industry leaders in hosted shopping carts would be Yahoo! Store, Volusion, BigCommerce and Shopify. Those are in order of market share rather than top rated. Any of these will work for most businesses unless you are at the enterprise level.
All of these platforms have lots of features and thousands of users. The best choice really depends on the different aspects of your business and products.
My preference is BigCommerce as it has a great admin, features and level of customization. With the exception of Yahoo! Stores all have a free trial so you can try them out and determine which you like best.