Although technically in beta stage, in it's latest incarnation Zoho Writer 2.0 is a rather appealing proposition. Zoho Writer is one of a suite of productivity and business tools. There is also a spreadsheet application (Zoho Sheet), a PowerPoint-like application (Zoho Show), and loads more.
Zoho Writer allows you to create, edit, preview, and print new documents from scratch. If required, your document can be exported to a variety of file formats including: .doc, .docx, .pdf, .odf, .rtf, .txt, .sxw, and .html.
If the document you need to work on is already in Word, or some other format that's just fine. Zoho Writer can import files in a variety of formats, similar to those it can export. There is an upload file size limit of 10MB which may pose a problem for very large documents - however, one could break the document up into several smaller files before uploading.
One thing I really like about the service is the provision of a Page View, similar to that in MS Word which allows you to work on the document in a more WYSIWYG (What You See Is What You Get) manner with the edges of the page visible on screen.
Finally, documents can be shared amongst individual users or groups of users with read or read/write privileges being assigned as required.
Zoho Writer is free and comes with 1GB of storage space. I haven't had to depend on this service yet so I can't say how it performs under stress but so far I'm very impressed. I created this blog post with it and uploaded it easily.
Zoho Writer is easy to use, flexible, well-featured, and (so far, at least) reliable.