In OutSystems Forge, there are a number of connectors to the most popular cloud services, like Facebook, Twitter, Zendesk, and Twilio. Some of these connectors come with a sample app so developer can try it out. Because the OutSystems visual editor is integrated with Forge it's easy to download and start customizing connectors.
Most of these components are built with OutSystems, using the SOAP web services and REST APIs provided by these popular cloud services. Some of the components also use extensions code (e.g. Cordova plugins, or backend code using the underlying framework libraries/SDKs). These components will get your developers started quickly.
But it is also possible for a team of developers to create their own - in fact, it is very common for an organization to create and share their own components.
The following list is just a sample of what is available; more components and connectors are added every week to the Forge.