Java Serialization @ JDJ: "Java Serialization
Lesson 7, Java Basics
By: Yakov Fain
In lessons 5 and 6 of this series, you've learned how to use some of the Java streams to read or write bytes, characters or numeric data. This lesson is about reading or writing entire Java objects into streams."
Good, quick introduction (approx 20 paragraphs) to Serialization and Externalization, plenty of examles and manages to cover performance issues etc...