The Xtra Easy version of the Database

Oracle Database XE

All I can say so far is that this thing rocks.

http://www.oracle.com/technology/products/database/xe/index.html

Simple to install.
Simple to manage – dead easy in fact.
And … simple to import data from Excel!

The Seminal Classloading Paper for OC4J

For anyone working with OC4J prior to the 10.1.3 release and interested in knowing more about the way in which the classloaders work, this paper addresses most of the questions I've ever heard.

http://www.oracle.com/technology/tech/java/oc4j/pdf/ClassLoadingInOC4J_WP.pdf