PowerPivot

[BigTimeHockeyMom]

What can PowerPivot do for your work on Excel and SharePoint?

[suwunk]

PowerPivot for Excel is an add-in to Excel 2010 that provides you with the capability to manipulate vast amounts of data using, integrate data from multiple data sources and share the results with others – with little or no assistance from IT
PowerPivot for SharePoint is nothing but SQL Server 2008 R2 Analysis Services running in Vertipaq mode within SharePoint 2010. Vertipaq is the in-memory technology that enables fast data manipulation in Excel Services and also enables efficient share & collaboration across your organization. In addition, PowerPivot for SharePoint offers IT administrators the ability to monitor and control self-service BI (when uploaded in SharePoint 2010) thru its IT Operation Dashboard
http://www.petri.co.il/what-is-powerpivot.htm

[auryn]

This may also help you:

PowerPivot for SharePoint (http://msdn.microsoft.com/en-us/library/ee210682.aspx)