Today Microsoft announced the general availability of the public beta of Office 2010, SharePoint Server 2010, Visio 2010, Project 2010 and Office Web Apps for MS customers and partners.
You can download the beta at
PowerPivot for Excel 2010 beta you can download from here:
After you install the product you can test it’s amazing functionality with using sample data , which can be downloaded from the following codeplex site:
PowerPivot Sample Data Download