Invitation and roundup from Aaron Nelson.
Reporting is a potentially huge topic so here are just a handful of ideas that might get you started:
- Server Performance Reporting
 - Technologies to help offload reporting
 - Reporting services tricks
 - T-SQL tricks for presentation and formatting
 - Database design considerations for reporting
 - Self-service reports
 - Reports for executives
 - Reporting from Oracle in SSRS
 
Don’t forget that the DMVs are pretty much qualified as ‘Reports’ so those count too!