Mural.ly, self described as GoogleDocs for visual people, is a free and user-friendly digital poster creation/team collaboration tool that resembles Prezi. The team behind this project comes from the gaming industry. They built this platform to offer a multimedia collaboration space to designers of all trades. Teachers can use this free platform to facilitate group work amongst students, create project templates or teach entire lessons. Users can drag and drop many kinds of media in their murals (text, sticky notes, shapes, images, videos, GoogleDocs, etc.). Using the insert comment function, you can start a discussion around a specific part of the mural, and even direct the comments to specific collaborators using the @ symbol. Mural.ly is a web 2.0 application and as such, you can make your murals private or public, share murals with colleagues, and set up individual permissions. Finally, all changes are tracked so that you always know who did what and when. The free version comes with unlimited murals and collaborators. The entry level license ($5/mo) lets you organize your murals in (class) rooms, export them as images (think poster presentations), and backup your murals as zip files. Mural.ly has less features than Glogster or Prezi but its streamlined interface make a very user-friendly platform.
For a demo, watch this video: