If you liked Etherpad (posted last week), then you will probably like Writeboard as well. Setting up a space is much like the other service: 1) Pick a name for your "board", 2) assign a password, 3) and give an email address. You can then email people you want to join, or in the case of a class, simply give out the URL and password so students can log on and begin collaborating.
The "tour" page lists the features of this web-app, and there are a few! For example, you (and others with the PW) can edit the writeboard, (or mark it), export it as plain text or email it. There doesn't seem to be a limit on the number of "invitees". Version tracking is quite good: every time you save a change to a writeboard, a new version of that writeboard is created in the sidebar. (They use an ingenious "dot" system to keep track of the size of the changes.) Not only can you merge and compare changes, but you can discuss the document by leaving remarks in the comments area.
And you can even "subscribe" to the writeboard in RSS and be notified anytime anyone makes a change.
