Graph of programming languages people used in 2012
I came across this link representing a visualization of programming languages usage based on a hashtag collect : http://www.ioncannon.net/projects/code2012/
Although this method can be criticized, it provides interesting data : JavaScript is the clear winner with Java just behind. We can see Scala is a growing language too, it has been used more than PHP last year (according to this study).
If you find another study on this topic don't hesitate to comment this blog post to let me know.