This online media album looks like a good tool for students and teachers. It holds all sorts of media (images, video, documents) and does allow commenting in a host of ways. In this example I used audio and doodling, you can also create and comment using video with your webcam. Voicethread is educator friendly offering k12 teachers a free "pro" subscription. With the pro account you can create "entitities" for your students. You can see a great project using voicethread here. It will be a great addition to use with the smartboard.
I will be trying this out with 2nd graders later this week.