Etherpad was a simple and great web-based application that allowed multiple people to collaborate on a single document. Google acquired the company that developed it and released the code as open source. As a result, several replica sites of the original Etherpad have emerged. Google is supposed to be incorporating this technology into their Google Wave platform sometime soon.
The interface is simple and elegant. A teacher or student needs to start the collaborative document space at site such as TypeWith.me or PiratePad.net. A link will be generated in the address bar and this URL can be emailed to the other collaborators. There is a space to enter the collaborators names, an option to assign a color to yourself to identify your contributions, and a space for live chat. It does not use user accounts, so co would have to export the document (or copy and paste the text) once the collaboration session has concluded.
It's basically a very stripped down shared Google document that is perfect for just-in-time collaboration. This tool might be great for a class to begin work on a collaborative note taking or document writing project that can then be later stored on Google docs (export or copy + paste).
Header photo by Robert S. Donovan