There are a number of OBEs available for the OWB 11gR2 release which range from an overview of all the cool new usability improvements in the mapping editor (auto-mapping improvements, copy-paste expressions, operators, operator groups, group/ungroup operators, spotlighting to name a few!), through basics of using the operators in a mapping for joining, filtering, pivoting and so on, then diving into building pluggable mappings (aiding reusability and good software design practice) and last but not least an OBE on data profiling covering profiling, deriving rules and even cleansing the data!
The entire Oracle OBE 11gR2 release OBE's are here(or search for OWB):
There are some interesting examples here, worth checking out to see some of the cool new features and existing ones that illustrate the capabilities! In the 11gR2 set there are other interesting posts well worth checking out such as the High Speed Data Loading and Rolling Window Operations with Partitioning post, all essential information for leveraging the database to the max in your ETL loads.