Unsorted links to different papers, presentations, etc.
SQL 101: Interpreting Query Execution Plans – Iggy Fernandez
Quick Wins in Optimized Analytical Processing Capabilities of 11g Release 2 – Husnu Sensoy
Cost Based Query Transformations – Riyaj Shamsudeen
Enhanced Subquery Optimizations in Oracle – Oracle
Cost-Based Query Transformation in Oracle (ppt) – CBO team