VoiceThread is a service that I had tried out a while ago and never posted about. It allows you to create collaborative multimedia slide shows using videos, images, text, and documents.
There is a free version for educators. If you want to have student accounts you need to subscribe to it.
The free version does have some great features and it is easy to use. Sign up for your free account, upload your media (documents, videos, images, etc) and then share your presentation. Views can comment on your presentation and you can even comment. The cool part is that comments can be text, voice, or even video. They can even use their phone to comment and they can doodle while commenting.
Here's an example. You can see who has commented and their comments while viewing the presentation.
This is a great way for teachers to create classroom presentations that are interactive and allow for feedback and commenting. The school license would also allow students to use VoiceThread for class projects and get real feedback.
Here's a great wiki by Jen Dorman on VoiceThread: http://jdorman.wikispaces.com/Voicethread
There are tips, lesson ideas, help, and more for using VoiceThread in education.
Try it out: https://voicethread.com/