37Signals' Writeboard is trying to derive some buzz off the recent interest in collaborative web editing, e.g. JotSpot Live or Writely. But Writeboard is in fact nothing new, but simply a 37Signals branded version of ... the wiki!
Yes. This is just a one page wiki with an edit history and a forced login to view/edit. There's no fancy rich text editing, it's plain old wiki-formatting once again. There are no collaboration features except what was already the case with a plain old wiki (reload the page to see other people's recent edits). It has less features than almost any wiki package I can think of. There are plenty of hosted wikis (or just look here).

Free is always nice, but this must be seen as a pure marketing effort to drive attention and interest to the products of 37Signals. 37Signals is of course "the Apple of simple web applications", so I'm sure they can manage to get product reviews out of this (oh wait, they have)