The title pretty much says it all…
SSRS 2008R2 can provide data feeds as a means of providing data to other applications. If you need to know more, perhaps start here: http://technet.microsoft.com/en-us/library/ee240754.aspx
PowerPivot (www.powerpivot.com) supports getting data from a variety of sources, including data feeds!
However, IF you’re hosting your report in a SharePoint library (via SharePoint integrated mode) AND that site is enabled for anonymous access, all you get is an error message when trying to connect to the feed from Excel.