Cacoo, a collaborative diagramming tool that I reviewed when it launched last year, has now left beta. Cacoo changed their pricing structure while leaving beta, but the good news is that they still have a free version and the free version offers plenty of functionality for most classroom uses. The free version allows for 15 collaborators on a diagram and up to 25 diagrams per account.

Cacoo allows you to draw shapes, type, and drag and drop elements of your diagram. One of the unique aspects of Cacoo is that you can also upload images to include in your diagrams. The collaborative aspect of Cacoo is that you can invite other people to contribute to your diagrams. Cacoo allows you to chat with your collaborators in real-time while you work on your diagrams. Watch the video below to learn more.

Applications for EducationFor students that are visual learners, creating diagrams can be very helpful in forming an understanding of concepts. I often use diagrams or mind maps in my US History classes to help students understand how multiple themes apply to a particular event. I can see myself having my US History students use Cacoo to contribute to the creation of diagram about the themes of post-Civil War Reconstruction.

Here are some related items that may be of interest to you: 
Bubbl.us – Free Mind Mapping Tool
Flock Draw – Simple, Collaborative Drawing
Lovely Charts – Create High Quality Charts