Official Documentation for the Core Java APIs.

http://www.apl.jhu.edu/~hall/java/Documentation.html

Java Guru FAQ - Java FAQs indexed by topics including networking, collections, threads, serialization, server-side development and more.

http://www.jguru.com/faq/index.jsp

Beginner Java Tutorial - A beginner java tutorial website covering basics of programming along with java source code.

http://www.techonvideo.com/category/programming/java/

Java Tutorials - 16 tutorials in all covering everthing from syntax to Swing GUI interfaces, java libraries and product distribution.

http://home.cogeco.ca/~ve3ll/jatutor0.htm

The Java Tutorial at java.sun.com - Sun's java tutorial is set up as a series of trails that cover the basics as well as specialized trails for topics such as collections, 2D graphics, JAR files, JavaBeans, JDBC, and more.

http://java.sun.com/docs/books/tutorial/

Free beginner and intermediate Java tutorials - Beginner and intermediate topics from hello world to networking with java.

http://www.javacoffeebreak.com/tutorials/index.html

Java Programming...From the Grounds Up - Short Java tutorial at WebDeveloper.com.

http://www.webdeveloper.com/java/java_programming_grounds_up.html

Java Optimization Tutorial - Make your code smaller and faster.

http://www.cs.cmu.edu/~jch/java/optimization.html