Below are five ideas/tools to help with discussions.
1) Google Moderator A nice little tool from Google. View a video on how you can use it in class here. An example of Moderator being used in real life here. (Click on View Questions to see items.)
2) Comment on YouTube Videos Without Having to Use YouTube Comments You can insert a YouTube video into a Google Presentation. Share the Presentation with students, giving them comment privileges. Now students can comment on the video using Presentation’s comment feature without having to sift through the sludge that is YouTube comments. Participants can also respond to each other using comment threads.
3) Blog Posts If you are using Blogger, students can easily comment on posts using the commenting tool available at the bottom of each post. Comments can be moderated by teacher before they go public.