Google’s Writely

Writely is an AJAX based online word processor acquired by Google in March.

Writely is collaboration friendly, can import Word documents, save to PDF, OpenOffice, Rich Text Format and zip.The system offers online storage and autosaves your documents every 10 seconds.
It allows bookmarks for long documents, spell check, tags, image insert and also post to blogging site like blogger.

Other online word processing services provider are zohowriter, thinkfree, glidewrite, rallypoint and writeboard.

You can check a comparison of some of this services by CNet