EDPuzzle is an excellent (and free!) online tool for adding interactive features to videos from a variety of sources. I like the simplicity of EDPuzzles interface.  After selecting or uploading a video from the teacher can crop it, add some recorded audio notes, and finally add open-ended or multiple choice questions. The crop function allows the teacher to focus only on the part of the video that is critical for the students to see and eliminates the need to have students fast forward to a specific part.  The audio notes are great for introducing the video, adding a teacher comment to something and a specific point in the video, or providing a few concluding remarks.  Once the teacher has added the desired comments and questions, the video is ready to be assigned to students.  In EDPuzzle, a teacher creates classes and assigns students to a class to watch a video.  This feature allows a teacher to track the time that individual students spend with the video as well as their responses to any questions added to the video.  Get started by visiting: www.edpuzzle.com