Realtime Board is a nice tool for hosting online, collaborative brainstorming sessions. I've featured the service a couple of times since its launch last fall. The service allows to work with any information and visual content on one board individually or with the team. You can work with images, videos, PDF-files, write notes and comment everything, use colorful post-it stickers and work with files from your Google Drive. Recently, Realtime Board added a free education version. The education version provides schools with all of the features of the Pro version for free. That means you can create unlimited private and public boards, have an unlimited number of collaborators, and 3GB of storage space.
Applications for Education
If you're looking for a free tool that your students can use to plan projects and create multimedia media mindmaps, Realtime Board is definitely worth giving a try. You can try it without creating an account.