As you have learned, for almost every type of content you can choose to connect an external content rather than using the CMS.  
Here is the non-exhaustive list of the different services connected to GoodBarber.

Article :

• WordPress
• TypePad
• WMaker.net
• RSS

Photo :

• Flickr
• Instagram
• WMaker.net
• FB Photos

Video :

• YouTube
• Vimeo
• WMaker.tv
• WMaker.net
• Dailymotion

Sounds :

• Soundcloud
• Podcast

Events :

• Facebook events
• Google Calendar
• iCal
• WMaker.net

Social networks :

• Facebook
• Twitter
• Instagram

Custom connectors :
For the more experienced, the custom connectors allow you, by following a detailed documentation, to create your own connectors to retrieve content present on a source for which GoodBarber would not have created a connector yet. 

No doubt that you’ll succeed in organizing the information for your users in the best possible way, all in the same app, and by mixing internal content (CMS) and external content (connectors) if you wish.