Free Oracle Resources
There are quite a few Oracle articles here as well as some pdf documents (some of which appear to be in German).
Free Oracle Tutorials and Free Oracle Training Lessons are available here
An Introduction to Oracle: Tutorial Series
Downloadable Oracle tutorials and examples in pdf and html format including and introduction to Oracle, introduction to PL/SQL, Oracle's data dictionary, introduction to Oracle and Java.
Using Oracle PL/SQL
PL/SQL stands for Procedural Language/SQL. PL/SQL extends SQL by adding constructs found in procedural languages, resulting in a structural language that is more powerful than SQL
Oracle Designer/2000 and Developer/2000
The objective of this tutorial is to expose you to some important features and tools of Oracle Designer/2000 and Developer/2000
Introduction to Pro*C Embedded SQL
Embedded SQL is a method of combining the computing power of a high-level language like C/C++ and the database manipulation capabilities of SQL. It allows you to execute any SQL statement from an application program.
Sameer?s Oracle Techniques
Oracle tips and tricks.
Oracle Express tutorial.
Oracle Database Web Resources
Huge list of resources.