Finally… And for free. I am singing in the rain about these new features in the Salesforce Spring ’12 release! Anyone who has written reports in Salesforce knows the new analytic tools are groundbreaking for those looking for true BI within the base-reporting tool.
Joined reports- My personal favorite and absolutely critical for anyone who wants to bring together several multiple objects into a single view. You can bring in data from several standard and custom reports that have a common parent object. For example, you would be able to pull together contacts with their affiliations and recent activity history into a single view.  
Cross filters- This allows us the ability to do simplified joins between parent and child right within the report designer using WITH or WITHOUT statements.  So for example show me only Accounts “WITH” activities. 
Data bucketing- Quickly applies a bucketed category based on your specific criteria without creating custom formulas. You could create a bucket on Accounts named Size where the # of employees determines of the Account is Small, Medium or Large.
A couple of notes
Even if you have been upgraded to Spring ’12 these analytic tools are not due for GA in production orgs until Feb. 12 2012.
If you haven’t already, you will also need to upgrade to the Report Builder to build the Cross filters and Joined reports.