VoiceThread is a wonderful tool for building interactive, collaborative presentations. The program allows users to create slides from previously created media, like a PowerPoint or an image, and then add comments by voice, text or visually annotating slides. The program is designed to help students collaborate, comment or ask questions about a classmate's presentation. They no longer have to be in the same building to collaborate on a presentation or learn from their peers. By removing the limitations of the physical classroom, students can find others outside of their own class who share an interest in similar topics and/or an approach to learning and demonstrating understanding.
This wiki does not require students to have an e-mail address and it doesn't have advertisements :)