BUZZWORD

A flash-based, online, collaborative word processor.  It's features are very similar to Google Docs (see Google Docs - Matt Holbrook  or Google Docs - Sara Marcus or Google Docs - Jerry Stapleton) but it just feels smoother and more web 2.0.  :)   

The two features I like best are 1) can invite people to be co-author with full rights, reviewer with commenting rights, or reader  and 2) commenting feature is easier to work with than Google Docs.

As with Google Docs, you can download any document. Downloadable formats include MS Word 2003, MS Word 2007, XML, RTF, TXT,  or HTML ZIP. 

The one thing I would change is the way in which invites are done.  Similar to Google Docs, you need to add everyone's email to invite them.  I'd prefer to be able to send a link to everyone and put a password on the doc so that only folks with the password could edit.

Try it out, I think you'll like it!