Oracle internals, debugging and undocumented features
I am sure most of you are already familiar with these resources but sometime we all forget where to look for quick help when is really needed.
I find these demos and tutorials very valuable .You can quickly find out what needs to be done to successfully implement particular feature without spending too much time digging Oracle documentation and other resources ( of course I strongly recommend reading Oracle Documentation before doing anything).
You can find them at Online Demos and Online Tutorials
Oracle 11g R2 is also included.