Web-based office suites have made a transition. While at first they simply imitated desktop applications in a Web browser, the new collaborative capabilities have developed new ways of working and studying, creating a whole new market in the web 2:0 environment. They've begun to grow away from simply imitating Microsoft Office to developing personalities of their own.
Google Docs, Zoho and ThinkFree appear to be the most popular web based office suites, and they have all been written about extensively on the web, so I'll save you from yet another comparison review! But from all the reviews I have read, in comparing functions and features, Computer World's review is the best one I have read so far. So have a read or judge for yourself to decide which one is best for you!