The latest version of Microsoft Office 2010 features collaborative editing so you and your team members can work on the same Word document or PowerPoint presentation simultaneously.
However, if you are not on Office 2010, you can still add real-time collaborative editing (or co-authoring) to your copy of Office 2003 or Office 2007 with DocVerse, a free plug-in from Google.
DocVerse lets users collaboratively edit Microsoft Word, PowerPoint and Excel spreadsheets over the Internet. The software also works offline so you can make changes to a document while you are in the plane and it will sync /merge the changes the next time you connect to the Internet.
All activity for every document is recorded into an activity stream which is viewable via Microsoft Office, any Web browser, or an RSS stream.