I ran into an interesting article the other day.

On more than one occasion, I've had to report against data held within a SharePoint list.  Each time, I've had to go out and query the SharePoint content database directly, which for obvious reasons, is completely unsupported.  In addition, as the lists evolved, I had to revisit each report to ensure it was still querying as expected.  Not the best solution by any means. 

http://www.jyhuh.com/blog/archive/2007/10/01/using_sharepoint_web_service_from_ssrs.aspx

The article I ran into illustrates using SharePoint web services as a datasource with Reporting Services.

I've seen discussion of using this approach, but never had any luck.  Finally, I've got an approach that in my toolbox when this need arises again.