The complete reference: Java 1.5
Thinking in Java - U can download e-book from www.bruceeckel.com
http://java.sun.com/ - Main page of Java website.
http://java.sun.com/developer/onlineTraining/ - has good online tutorials.
You can also visit http://forums.java.sun.com and become a member. Start answering few questions and look for beginner problems faced.
Also posted @ http://cmohan.spaces.live.com/blog