Source: http://feeds.gawker.com/~r/lifehacker/full/~3/q8QxcEAlnqY/icloud-takes-your-computing-to-the-web
We've talked about cloud operating systems before like EyeOS and Glide. iCloud shares "webtop" roots with them, bringing the experience of desktop computing to your web browser. Once you sign up for a free iCloud account, you're ready to start exploring the dozens of applications and widgets. You can edit documents in a Word-compatible editor, maintain a calendar, write emails, and tackle other computing basics. There's a photo organizer and media player, and the Vista-like sidebar can be customized with a variety of widgets to suit your workspace—your first order of business will probably be replacing the "Last Users Online" widget with something more useful.
iCloud is currently in beta. While it lacks some of the meatier features found in previously reviewed webtops, it does provide a completely mobile and relatively distraction-free work space. According to the iCloud team, it's best suited for use in Internet Explorer. You can—and I did—use it in Firefox, but support for Firefox is considered experimental. iCloud is a free service and (technically) requires Internet Explorer with Java Script installed.