Oracle PL/SQL Programming 2nd Edition 
 by Steven Feuerstein

This book is number one on Amazon's Top Ten books for Oracle Developers. 
I have read the second edition of the book. But the third contains some coverage 
of new object relational features that I feel are important. There are just a few examples 
presented in the context of Oracle forms. The author has a great deal of experience 
using PL/SQL. He gives a very thorough coverage of using the PL/SQL language and 
includes practical, usable code examples for each important aspect of PL/SQL including 
datatypes, cursors, dynamic sql, procedures, packages, functions, collections, OO objects, 
and calling external procedures. It would be helpful to understand the basic's of PL/SQL 
before starting on this book. But, all of that information is presented in the book
for the patient reader. The author uses a very relaxing and enjoyable style
with just a little bit of humor. The best book on PL/SQL I know of.