http://www.javaalmanac.com - The online counterpart of the Java Developer's Almanac - highly recommended for quick code snippets, and if you like the site, buy the book.

http://www.onjava.com - O'Reilly's Java website. New articles weekly.

http://java.sun.com - The official Java developer website - new articles posted weekly.

http://www.developer.com/java - Java articles hosted by Gamelan.com

http://www.java.net - The Java community website hosted by Sun Microsystems.

http://www.builder.com - Cnet's Builder.com website - All tech articles, some Java-centric.

http://www.ibm.com/developerworks/java - IBM's Developerworks; the Java section.

http://www.javaworld.com - One of the originals. Weekly updates of Java articles.

http://www.devx.com/java - Java articles hosted at DevX.

http://www.fawcette.com/javapro - The JavaPro online magazine website.

http://www.sys-con.com/java - The Java Developers Journal online magazine website.

http://www.javadesktop.org - The desktop Java community hosted at Java.net.

http://www.theserverside.com - Often considered the resource for all discussion server-side Java specific.

http://www.jars.com - The Java review service. Covers frameworks and applications.

http://www.jguru.com - A great source for Q&A style interaction in the community.

http://www.javaranch.com

http://www.ibiblio.org/javafaq/javafaq.html - The comp.lang.java FAQ - questions asked, answered, and categorized from the comp.lang.java newsgroup.

http://java.sun.com/docs/books/tutorial/ - The Official Java tutorial from Sun - very useful for almost any feature set.

http://www.javablogs.com - Blog aggregator for the most active Java-based blogs throughout the internet.

http://java.about.com/ - Java news and articles from About.com

Some more added to the list..

http://www.javaspecialists.co.za/ The Java Specialist Newsletter.

http://www.eclipse.org/ Eclipse main site.

http://www.javazoid.com/

http://www.esus.com/ Java Tips and Tricks


best open source java projects site

http://www.java-source.net/

which class in which jar?

http://www.jarhoo.com/

some more cool sites

http://www.thauvin.net/linkblog/

http://www.clientjava.com/blog/

http://javarss.com/

http://www.javaskyline.com/ Dedicated to Java.
http://semanticdb.blogspot.com
For testing your java code /Fragments /JSP

http://zamples.com/JspExplorer/index.jsp
Some more sites which I think can add value to your Java Knowledge

http://www.beginner-java-tutorial.com

http://www.java-swing-tutorial.com

http://www.jdbc-tutorial.com

http://www.beginner-java-tutorial.com

www.intelligentedu.com(for free it related e-books download)

www.precise.com

www.coolinterviews.com

www.java2s.com

www.virtusa.com

www.laliluna.de

www.roseindia.net

www.exampledepot.com

www.theserverside.com

www.techtarget.com

www.java-tips.org

www.artima.com

www.javafaq.nu

www.javaworld.com

www.pdfhm.com

www.raphidshare.com

www.buzzword.com