In YouTube there is an option to start a video at a specific point. Under the sharing options on a YouTube video there is an option to select a start time for the video. Unfortunately, there is not an option to select an end time. See the image below for a look at the time-stamped sharing option in YouTube.
Vibby is a service for breaking YouTube videos into segments and inserting comments into those segments. To segment a YouTube video on Vibby simply grab the URL for the video and paste into the Vibby editor. Once inserted into Vibby you can highlight a segment on the video timeline. Vibby then play only the sections you've highlighted. Click on a highlighted section to add a comment to it. Videos edited through Vibby can be shared via email, social media, or embedded into a blog or website. Click here for a Vibby tutorial.
EDPuzzle is a neat tool that allows you to add your voice and text questions to educational videos. On EDpuzzle you can search for educational videos and or upload your own videos to use as the basis of your lesson. EDpuzzle has an online classroom component that you can use to assign videos to students and track their progress through your video lessons. Within EDPuzzle's editor you can select portions of videos for students to watch. EDPuzzle offers the option to share your videos to Google Classroom. In the videos embedded below I demonstrate how to use the main features of EDPuzzle.
Vialogues is a free service that allows you to build online discussions around videos hosted online and videos that you have saved on your computer. You can choose to use all of a video or portions of a video. Registered users can upload videos to Vialogues or use YouTube videos as the centerpieces of their conversations. After you have selected a video from YouTube or uploaded a video of your own, you can post poll questions and add comments that are tied to points in the video. Your Vialogue can be made public or private. Public Vialogue's can be embedded into your blog or website.