Sharing a workbook enables more than one user to view and edit the data at one time, which is useful in group projects in which each member has a distinct area of responsibility.
Sending files by e-mail is a very efficient means of collaborating with colleagues.
Adding comments to cells is a quick way to let your colleagues know what you're thinking without taking up valuable space in a cell.
Use the Go To Special dialog box to find cells with special contents, such as comments, constants, or formulas.
Tracking changes is vital when you share responsibility for a workbook with several other people.
When your workbook's data is too important to leave lying around in the open, use passwords to protect all or part of the file!
Authenticating workbooks with digital signatures helps to identify the source of your files, so you won't have to guess about the origins of that next attachment in your e-mail inbox.
Saving a workbook as a Web-accessible HTML document is as easy as saving it as a regular Excel 2007 file, and opening a workbook saved for the Web is just as easy as opening any other Web page.
Use the AutoRepublish facility to update Excel 2007 files on the Web. Whenever anyone changes the original workbook, Excel 2007 writes the edits to the HTML version of the file.