Twitter Accounts to Follow:

@javacodegeeks ~ These guys share some great stuff. Do follow them.

@java

@virtualJUG

@zeroturnaround

Facebook Groups To Follow:

https://www.facebook.com/ilovejava/

Meet Up Groups to Follow:

JUG (Java User Group in your City)

Virtual JUG ~ This is a virtual JUG that is entirely online. They frequently have presentations from top speakers in the Java community

Java Websites to Follow: You can check the following sites once or twice a week and make time to read any interesting articles.

www.javacodegeeks.com ~ The above twitter handle belongs to this site

www.ibm.com/developerworks/learn/java/index.html

www.developer.com/java/

http://www.baeldung.com

middlewaresnippets.blogspot.in

dzone.com

javamex.com

infoq.com

www.javaworld.com

www.techcrunch.com ~ This is generic news site related to software industry. My advice is to follow it regularly like once a day. 

http://java-performance.info ~ Specific to Java performance

https://www.geeksforgeeks.org ~ Seems to have lot of articles on Java and other programming languages and even other software engineering areas. Seem to include lot of practice questions for both general coding as well as interviews.

http://www.lambdafaq.org/ ~ Seems like a really good resource for Lambdas