I did some demos recently at a SharePoint event @RealDolmen last week and one of the things I demoed was PowerPivot – a technology not specifically linked to SharePoint but it can be integrated. So here goes my PowerPivot elevator pitch:
PowerPivot is a separate add-in for Excel which adds an in-memory cube which allows you import enormous quantities of data with incredible speed into Excel from different data sources. You can define relationships between these data sources and parse through this data using pivot tables, pivot charts or using the new Data Analysis Expressions (DAX).
If you want to learn more about PowerPivot definitely take a look at PowerPivot Component Architecture which is an excerpt from the Microsoft SQL Server PowerPivot Planning and Deployment technical white paper.