One of my favourite Captivate third-party widgets is the Interactive Drag and Drop Widget from Infosemantics. As the name implies, this widget provides something that is unfortunately missing even in the latest Captivate release (v6) – the ability to create drag&drop interactions as part of a quiz.
The folks at Infosemantics have done a great job providing detailed info on how to configure the widget (no need to repeat this info here) and also show some examples.
When I first started using the widget, I built a small set of samples, the Flash version is available here and a video recording can be viewed below.
Hopefully, this functionality will be available soon for HTML5 publishing!