Although Office Web Apps have been around for a little less than a year, Microsoft's latest offering, dubbed Office 365 includes Office Web Apps, Sharepoint, Lync Server and Exchange Server.
This is a business-grade offering that includes uptime service level agreements, backups and other security related features. It is akin to a free version of Gmail/Docs and the paid Google Apps platform.
These services are all hosted on Microsoft's servers on the cloud so no software other than a browser is required to use these web applications.
You still have the option of running a copy of Office, which is included as a subscription option, but at the end of the day almost all the tasks you can perform with Office on your computer can be performed within a browser on the cloud.
So if you are looking to move your small business to the cloud and let someone else deal with the headaches associated with running an IT department this may be a great option for you.
Announcement via Microsoft Office Blog.