Core Web Programming
In-depth Java 1.1, plus dynamic HTML, CGI, and JavaScript 1.2 in a comprehensive 1400 page reference from Prentice Hall. Web site includes table of contents, source code archive, on-line chapter, and reader reviews.
Essential Java Style : Patterns for Implementation
Learn about design patterns, and improve your Java programming skills with this great style guide.
Java in a Nutshell
Popular fast-moving tutorial from O'Reilly, aimed at experienced programmers.
Sun's Java Tutorial
On-line version of book from Addison-Wesley.
The Design Patterns Java Companion
Free online book by James W. Cooper. Also it can be download in PDF format. Examples.
The Java Cookbook: Solutions and Examples for Java
Book by Ian F. Darwin provides solutions to many problems that Java-developers need to solve regularily. The authors site provides errata, download of all code samples and further information about Java.