HC is a bit lean on programming discussion, so I was happy to come across your post.
Languages I've came across "in the wild" are Python (PANDAS), C++ (BOOST) and just any type of general scripting. Google Scholar is great for learning this stuff too (but the subject matter can be heavy).
I'm a programmer by trade, and in the last year or two I've been researching financial coding, and how I can migrate my abilities from traditional IT into something FinTech as I am chasing a career change.
It's of my opinion that FinTech will become huge in the future, so it'd be better to train up now so you can hit the ground running.
If you're interested, I've also started a project to develop an opensource algorithmic trading platform, called Shark (https://github.com/danielneil/Shark), which I've used as a learning aid in order to become a better a quant, and at the bottom of the page I've listed the technology stack I've used.
