Official Java and JEE

Java Technology Reference

Java Standard Edition (JSE)

Java Enterprise Edition (JEE)

The official Java tutorials

The official JEE 7 tutorial

JEE 7 Technologies index

Java language spec and JVM spec

Java community

Oracle Java community

OpenJDK

Java Community Process (JCP)

Apache Commons

Apache.org Java projects

JBoss.org

Spring

Google Guava

Trending Java projects on github

JEE and Java web servers

Apache Tomcat

JBoss Wildfly

Glassfish

Build and test automation

Sonatype Maven books

Jenkins documentation (wiki)

JUnit reference documentation

Source and version control

The SVN reference book

Git reference documentation

Java IDEs

Intellij IDEA documentation

Eclipse documentation

Netbeans knowledge base

Vim configuration for Java coding