So, i'm sure you have heard of Google Wave. (If not, here)
However, the hype about this promising open source tool by Google, does not yet reflect its capabilities. As a developer, i have been using Google Wave for quite a while now, and the promised "real-time editing" of a document by several participants may be a neat feature, but editing an actual document (e.g: .doc, .docx, .txt) is not possible within this tool.
Participants in a wave may only edit the wave itself, not an open document (opening a document inside a wave is not possible). And, unfortunately, the rich text formats and writing options of a wave are very limited. So, working on an existing document, or copied content of one is practically impossible if it contains more than just simple text.
I would love to see Zoho make its way into Google Wave as an API (extension) so this could be made possible!
Writer is a powerful online word processor, designed for collaborative work.