Here are some of the high voted answers:
How to pass parameters on onChange of html select
Remove substring from the string
Difference between plugins and Ruby gems?
java.sql.SQLException: No suitable driver found for jdbc:microsoft:sqlserver
Adding one month to current date?
On StackOverflow - focusing (or atleast that's the intention) on :
Back End: Core/Enterprise Java (Concurrency, Collections), Advanced SQL, Hibernate, Spring(AOP, ORM, IOC, MVC, Security, Enterprise Services), Stored Procedures, Load Balancing, Failover, Clustering.
Android Mobile Platform: Android SDK (https://groups.google.com/forum/?fromgroups#!forum/android_learning)
Functional Programming: Groovy
SOA: Web Services (SOAP/REST), Spring REST and related stuff
Front End: Java FX, Java Web-Mobile Components, MVC (Spring, Struts), Ajax, HTML5, Native JavaScript, JFreeChart, RIA, Jquery, CSS, JSON, JSTL, Tag Libraries.
Networking,Administration: Linux Kernel Services/Configuration, Linux Filesystem/Package/Account Management, TCP/IP, NFS, Clustering, Opsview.
Big Data: Hadoop
Data Science: Github
Cloud: AWS
No SQL: MongoDb
Algorithms: Divide & Conquer, Graphs, Data structures(Heaps, Hash tables, Search trees), Randomized algorithms
Scripting: Bash, Shell, Excel VBA.
Search Engine Technology: Lucene
Project Management: Agile, Scrum.
OS: Ubuntu, Windows.
SCM: Configuration Management(Maven ,Ant), Continuous Integration.
Other: XML Technologies, Apache Libraries

Interested in learning more about JVM Languages/Functional Programming(Scala, Closures), No-Sql Databases, Search Engine technologies(SolR), Cloud Computing, Web 2.0 Frameworks (RubyOnRails, Groovy On Grails, Play Framework), Mobile Development\Frameworks (Apache Cordova), Agile/Scrum.