I’m working on a presentation for the GPUG Summit that looks at PowerPivot and Dynamics GP. If you’ve been want to play with PowerPivot, check out the PowerPivotSamples from the Microsoft Download Center
Download: PowerPivotSamples – Microsoft Download Center
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.