Links to external resources on the web. As always, I welcome suggestions if anybody's got a link to another site that they think would be useful.
Core Java Website - the website that corresponds to your book.
Code samples from your book (fully updated) from the above website.
java.sun.com - Official Sun website.
Java API Documentation from java.sun.com.
The Java Tutorial from Sun's website. Learning the Java Language is a good place to start.
Code Samples from java.sun.com. You'll probably be most interested in the J2SE examples.
Coding Conventions used in Java. Mostly naming conventions (MyClass, myMethod) and stylistic conventions (bracket placement) used in Java programming. None of this stuff is mandatory, they're just common conventions which makes everybody's code more readable.
IBM's Java Website - developer tools, news, docs / tutorials, links, etc.
Gamelan a pretty serious Java-developer website.
Java Lobby A Java-advocacy site. They post news, announcements, editorials and -- oh yes -- code.
IBM's Java technology Articles and columns
A review of Java Performance Tuning on Slashdot.org. Explains how to make Java programs run a little faster.
New features up-and-coming in Java 1.5 as told in an interview with Joshua Bloch (Sun Engineer).