If you haven't seen it yet, check out AjaxWrite, a pure AJAX driven word processor. A cursory look shows it to be pretty interesting with functionality that is on par, if not a bit better, than Outlook Web Access (OWA). Of course, the caveat with OWA is that you need to be using Internet Explorer to really get the slick things to work. The "normal" version that plays nice with multiple browsers isn't nearly as slick as AjaxWrite, but then again, AjaxWrite only works on Firefox 1.5+ and currently relies on XUL for some of its functionality.

It appears that AjaxWrite is an attempt to make money through software as a service. While the current version is free, the site hints at eventually charging for greater functionality and storage. I suspect that they have a fair amount of work to go before they'll be able to charge for the resource, but the first release is impressive enough to keep an eye open.