New videos and slides on SQL Server 2008 R2 and PowerPivot
Two big resources on SQL Server 2008 R2 and PowerPivot just came out lately. The first is the videos and slides from BI track in TechEd 2010 in New Orleans. You can download all the slides and video recordings on the sessions that you want (and you can use the "list" view for quick and easy access). This one is free for everyone.
Another resource that is free, but requires registration, is 24 Hours of PASS. Registration to PASS is free and very recommended as it gives you access to a lot more information and resources. 24 hours of PASS was given with also top notch professionals as part of the SQL Server 2008 R2 Community Launch.
Both sites offer a lot of material both for BI developers and DBAs on SQL Server 2008 R2 and PowerPivot – so if you're interested in any of the subjects, go and check them out.