We collect data on people starting/completing clickstarts.
This obviously is limited to the collection of clickstarts we have - but that is now fairly extensive. This is possibly a reasonable indicator of what people would be interested in the future - as this corresponds to new applications being created and people "kicking the tyres"
Summary: The old faithful Tomcat7 holds strong - Play2 is popular as always. Close behind - Javascript is to be seen: Node.js and Angular.js in particular.
Enjoy!