I have just read Office 2.0 by Ismael Ghalimi, from IT | Redux - his post is a a great lead into the world of Office 2.0 applications.
Office 2.0 applications enable users to use software online instead of software installed on their desktops. There is now an impressive variety of such applications. Thanks to this list compiled by IT | Redux, you now have access to an extensive directory of Office 2.0 applications with corresponding links to application web sites and reviews by Solution Watch, TechCrunch and IT | Redux.