Entri is a free document collaboration tool that doesn’t require registration to use. Entri’s goal is to make document collaboration as quick and easy as possible. To start a document on Entri, just click the big “create your entri” button. Entri assigns your document a unique url that you can share via email or with Twitter. Once your document is developed to a point at which you no longer want it edited by other, click the “lock” button to prevent any further changes by others.

Applications for Education
Entri could be a convenient tool for students to quickly take notes as a group, record brainstorming sessions, and create outlines.

Here are some related items that may be of interest to you:
Titan Pad – An Ether Pad Clone
Primary Pad – An Ether Pad Alternative