Effective Java - Joshua Bloch, [Addison Wesley], 0-321-35668-3]
Java Programming Language - Arnold, Gosling, Holmes, [Addison Wesley], 0-201-70433-1]
Code Complete - Steve McConnell, [Microsoft Press], 0-7356-1967-0]
The Pragmatic Programmer - Andrew Hunt, David Thomas, [Addison Wesley], 0-201-61622-X]
Design Patterns - Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides, [Addison Wesley], 0-201-63361-2]
Designing Web Usability - Jakob Nielsen, [New Riders], 1-56205-810-X]
Java Platform Performance - Steve Wilson, Jeff Kesselman, [Addison Wesley], 0-201-70969-4]
Refactoring - Martin Fowler, [Addison Wesley], 0-201-48567-2]
C++ FAQs - Marshall Cline, Greg Lomow, Mike Girou, [Addison Wesley], 0-201-30983-1]
Practical Java - Peter Haggar, [Addison Wesley], 0-201-61646-7]
Effective Enterprise Java - Ted Neward, [Addison Wesley], 0-321-13000-6]
Patterns of Enterprise Application Architecture - Martin Fowler et. al., [Addison Wesley], 0-321-12742-0]
JSE 6 All Docs - Sun Microsystems
JSE 6 New Features - Sun Microsystems
JSE 6 API (Javadoc) - Sun Microsystems
JSE 6 SDK Tools - Sun Microsystems
JEE 5 API (Javadoc) - Sun Microsystems
Java Language Specification - James Gosling, Bill Joy, Guy Steele, Gilad Bracha
Java Virtual Machine Specification - Tim Lindholm, Frank Yellin
java.net - Sun Microsystems
Javadoc Style Guide - Sun Microsystems
Java Look And Feel Guidelines - Sun Microsystems
java.sun.com - Sun Microsystems
java.sun.com - Articles - Sun Microsystems
java.sun.com - Tech Tips - Sun Microsystems
TheServerSide - The MiddleWare Company
JUnit Testing Framework - Kent Beck, Erich Gamma, Open Source
Ant Build Tool - Apache
JavaCC Parser Generator - java.net
Java2HTML - Jason Shattu
Tomcat - Apache
HTML 4.01 Spec - W3C
HTML Validator - W3C
CSS Spec - W3C
CSS Validator - W3C
Web Site Security Guidelines - Open Web Application Security Project
J2EE Design Patterns - Sun Microsystems
Portability Cookbook - Sun Microsystems
paulgraham.com - Paul Graham
Joel On Software - Joel Spolsky
Creating Passionate Users - Kathy Sierra
Artima.com - Bill Venners
Java Community Process - jcp.org
developerWorks - IBM
Focus On Java (About.com) - Java portal with original articles, free source code, and tutorials.
JavaRanch - A Friendly Place For Java Greenhorns
Java Almanac - Patrick Chan
jarhoo - WebtrexIT - ClassNotFoundException? Lookup jars and apps given class name
FindBugs - Bill Pugh, David Hovemeyer, Brian Cole, and others - Great tool, finds bugs
Java Theory and Practice - Brian Goetz articles on IBM site
Regular Expression Builder - FileFormat.info
Java Programming Forums - Jelsoft
Java Concurrency in Practice - Brian Goetz, et al, [Addison Wesley], 0-321-34960-1]