Useful links to various development reference and resource sites:

Java J2SE
java.sun.com	Sun's main Java site for developer
Java Tutorial	Sun's Java tutorial
Java Language Spec	Java Language Specification 2nd edition
Java VM Spec	Java Virtual Machine Specification
1.5 API docs	Java J2SE 5.0 (1.5) API documentation online
1.4.2 API docs	Java J2SE 1.4.2 API documentation online
1.3 API docs	Java J2SE 1.3 API documentation online
1.2 API docs	Java J2SE 1.2 API documentation online

Java J2EE
EJB3.0	JSR220 - EJB3.0 specification
J2EE 1.4	J2EE 1.4 documentation
J2EE 1.3	J2EE 1.3 documentation
J2EE 1.2	J2EE 1.2 documentation
Sun Blueprints	Sun's Java Blueprints (Patterns) for J2SE, J2EE, J2ME and platform performance

Java Community websites
JavaLobby	Java news and discussion forums
Sun Java Forums	Java Forums - great resource to ask questions and find answers to Java Platform problems
JavaBlogs	Weblog aggregator for a huge number of community Weblogs (including my own) covering all aspects (news, discussions, product reviews & releases) related to Java Technology
Eric Thauvin's Blog	Great blog for Java industry related news and headlines, product release news etc. Eric's blog headlines are regularly featured on the front page of the Java Developer's Journal website.
TheServerSide	J2EE and Java technology news and discussion website.

HTML

JavaScript

Software Development - General