Document Sharing - applications

There are quite a few sites which offer applications for sharing and collaborating on documents, these are the sites that I have tried on different occasions, if you know of more please add:
GoogleDocs - online collaborative word processing
http://docs.google.com
YourDraft - Online draft - shared editing - No registration neccessary
http://www.yourdraft.com
WriteWith - online collaborative word processing
http://writewith.com/
Zoho Writer - online collaborative word processing
http://writer.zoho.com/
WriteBoard - online collaborative word processing
http://writeboard.com/

The applications share similarities and differences. So far I have found google docs very useful for working with my team - it enabled us to build and refine our curriculum online, from home, instead of spending extra hours in school.

I hope next year to use google docs with my students for both individual and group work.