To help you with learning PL/SQL, try Oracle Database 10g PL/SQL Programming by Scott Urman, Ron Hardman and Michael McLaughlin. I have been using this book for a couple of months. This book has helped me with answering questions for this Web site. Although 10g is in the title of this book, it also can be used as reference book for 9i users.
This was first published in August 2006