Shared Information

You can share an excel workbook.

Not exactly realtime but it can then be opened and edited by several users at the same time. Changes made to the saved document are updated when you save your copy. If you have had the document open for a while and want to see changes other users have saved, just resave the doucment. Other user changes will be outlined so you can see what has changed.

Share a workbook
Create a workbook you want to make available for multiuser editing, and enter any data you want to provide.
If you want to include any of the following features, add them now: merged cells, conditional formats, data validation, charts, pictures, objects including drawing objects, hyperlinks, scenarios, outlines, subtotals, data tables, PivotTable reports, workbook and worksheet protection, and macros. You can't make changes to these features after you share the workbook.

On the Tools menu, click Share Workbook, and then click the Editing tab.
Select the Allow changes by more than one user at the same time check box, and then click OK.
When prompted, save the workbook.
On the File menu, click Save As, and then save the workbook on a network location accessible to the intended users. Use a shared network folder, not a Web server.
Check any links to other workbooks or documents, and fix any that are broken