Programming Languages I Am Learning / Working With

1. C/C++
• Systems (Linux, Android, Chrome) Programming 
• Efficiency. Memory manipulation. Complete control over the environment. 
2. Go 
• Systems, Concurrent and Networked Programming 
• Static Typing
• Faster compilation 
3. Java 
• Managed Code
• Android Application Development
• Open Source Libraries and Frameworks
4. Scala 
• A blend of all the features you ever saw in different languages! 
• Tries to answer “So, if we want to let programmers implement this feature as language library rather than language syntax, what features do we need to introduce in the language?” 
• Features:
• Actors Library 
• Operators as Functions 
• Flexible syntax (Prefix, Infix, Postfix mixing) 
• Makes Scala DSL friendly and "scalable".
• Makes the core language small (rest of the features are implemented in the library). Lisp Philosophy. 
• What happens when you try to fuse OOP and Functional Programming on JVM? 
• Static Typing and Terse syntax
• Concurrent and Distributed Programming
5. Clojure 
• Lisp on JVM
• Metaprogramming (Programmable Language) 
• Functional Programming
• Concurrent Programming
6. Python 
• Rapid Development
• Open Source Libraries and Frameworks
7. JavaScript 
• Web Front-end (with HTML5 & CSS)
• Object-based Programming 
• Node.JS
8. R 
• Statistical, Numerical Computing 
9. Haskell
• Purely Functional Programming
10. Erlang
• Fault-tolerant Real-time Parallel Distributed Computing
• Modifiable without downtime

Current Preference

If you need complete control over the environment, go down to C++. Otherwise, use Scala, Java, Clojure.