Google allows you to author documents and spreadsheets online. All you need is an account to access them. At first it only looked like Google was targeting consumers, but they've also been working on Google Apps for Your Domain.
According to an article on businessweek.com:
Google Apps for Your Domain lets companies offload e-mail systems to Google while keeping their own e-mail addresses. Soon, it's expected to add word-processing and spreadsheet services to the suite, which includes an online calendar, chat service, and Web page builder. In coming weeks, Google Apps will turn into a real business as Google begins charging corporations a subscription fee amounting to a few dollars per person per month.While Google has no where near the large scale B2B expertise that Microsoft has in terms of delivering applications to businesses, companies like Pixar and its parent, Disney are considering the switch. Others are sure to follow.
Of course, until all of us have some nanotechnology integrated into our weak flesh and transistor-less brains and are able to be online ALL THE TIME, users will need to be able to establish a web connection using their personal computing devices to use web-based tools. Which means that if you're that guy who likes to fill out expense reports while going through a BART tunnel, you might be out of luck with accessing your files on Google Docs.