It is hard to assess what the most popular programming languages are because there are multiple ways to measure them, but none of them are perfect (i.e., repositories, lines of code, occurrences in job offers, etc.). For example, if you work with embedded systems, C is very popular, but if you work on the web, the story is very different.

One interesting measure of a language's popularity is the number of questions asked about it. Stack Overflow features questions and answers on a wide range of programming languages and compiles a list of the most popular tags, with a breakdown by total, today, and this week.

This data is a nice proxy for how popular the different programming languages are.