Microsoft Office offered document collaboration through co-authoring support in Office 2010. You can also use Sharepoint server for document collaboration. Today Office Web Apps announced the availability of co-authoring support in Office Web Apps too. You don’t need an Office 2010 Windows app to collaborate documents among different authors.
We designed co-authoring in the Word Web App on SkyDrive accordingly: When you’re co-authoring, you always have a real time view into who is making changes and where these changes are occurring. As soon as you begin typing, the corresponding section of the document is locked and others are notified, placing you in control and freeing others from distraction. Contributors can hit “save” at any time to see an updated view of all changes.