Community Building includes forum systems (also known as bulletin boards), guestbooks, and mailing list applications.
Web based business applications include e-commerce systems (also known as shopping carts) for managing sales websites, Customer Relationship Managers (CRM), customer support systems, and project managers.
(Note: You are not allowed to make money from a MiddCreate site, but you can try out the e-commerce apps to see how they work.)
Surveys and Statistics includes different statistical applications that enable website traffic to be monitored and analyzed, and polling and survey applications can be used to query the views of website visitors.
Contact forms, clocks, e-cards, URL shorteners, and other novel applications.
More information (including how to install applications) here.
Files, databases, metrics, and a lot more. See more here.