A few weeks ago I came across what might be the best intermediate introduction to PL/SQL I have ever seen. While it is no substitute for the writings of masters such as Steven Feuerstein, it covers some essential aspects of PL/SQL and it clarified concepts such as block scope and dynamic cursors.
Doing SQL from PL/SQL: Best and Worst Practices
The Google html-ized version is available here
Allan's Musings 