Java, PHP, HTML/CSS, Python, JavaScript, C, C#, C++, LUA, XML/XPATH/XSLT
Java
Very little experience, I made a mobile application using it. Most of the syntax was copy, pasted, and modified. I don't know the syntax or how it functions to an in-depth level.
PHP
Used it for a server side language during a database course, to connect to MySQL and run query statements for a web page. Interesting fact for the people that didn't know, you can use a huge portion of your knowledge in C in PHP. PHP was built using the C language, much like a lot of other languages, and you can use the same syntax. If you put in a PHP section on your HTML web page, you can use "echo" or "printf". Make sure you put in "printf("InsertText"); Test it out sometime if you are interested.
HTML/CSS
It is very rare that you will find a programmer that doesn't know these a little bit. They're very human readable, and all universities cover them. Even if you are a self-taught developer, I'm not sure why you wouldn't start with understanding how web pages are developed.
XML/XPATH/XSLT
This language is an orgasm language for web developers that know it's capabilities. XML is used for so much software, yet no one hears about it. You use XML to build Word and Powerpoint documents, to run your videos and to display your images using applications on your OS. It is HTML, but it describes data rather than displaying it. HTML display data using preset tags like <body> and <title>, etc. XML is built using the same tagging concept because it is a markup language, except it describe the data using tags made by the developer. If you are going to show a person's name, you can put their name like this example below:
<firstName>John</firstName>
<lastName>Doe</lastName>
That part is super simple; you are putting everything within descriptive tags. Now, here comes the part on why it's not used more often for the internet. It is tedious to place a family tree accurately within an XSLT, which is comparable to CSS. The interesting part is that XSLT is capable of supporting scripting concepts to change content dynamically.
People find this too difficult to work with because web developers want their job to be faster. XML/XSLT is a much more efficient way of creating a web page if the time is spent developing it in this manner. The best part is that you can apply XPATH which is a querying system to pull information out of a web page. This can be used to put out accurate information within a document and then use it within a variable or function.
If anyone is interested in testing it out, it is very easy to get the basic understanding after a few tutorial videos on YouTube. Check it out and I'll throw out another tip. You can create XHTML transitional web pages that use both XML concepts and HTML, but you'll have to do a few extra things to make your page work.
Python
Tested out this language using a program called Sikuli. It is an image recognition IDE that always you to capture pictures and then program in Python functions. I used it to automate a few Facebook games, back when I was obsessed with them.
It's a very simple language, but you have to use programming grammar and most people don't even to use English grammar!
JavaScript
This is very powerful language favored by web developers with all of their frameworks like Angular. I've experience building simple web applications, but I don't have much experience with the frameworks.
C
My first real programming language. I learned this around three years ago, building tedious programs for my Introduction to Programming course. My god, that was an awful experience. Used this language to create several programs to output a ton of bullshit into the command prompt. It's probably one of the most dominant languages you can use.
C++/C#
I'm combining this one for a particular reason. Why does the poll have C and C+ + together, but separates C#? I've used C++ in a visual programming course, using the Visual Studio 2012 IDE. It was a language easily picked up due to my knowledge in C, but I've always been under the impression that C# has very similar syntax. Whenever I have seen programs written in C#, I was able to read them relatively easy. I guess that is just because the basic syntax is almost universal, the logic of loops and functions work pretty similar. If someone has the time, I would be glad to hear about the significant differences.
LUA
This is an easy scripting language used for game development. You should learn this if you are interested in that field. I have a little experience modifying LUA files for a Forsaken World private server. You'll also find these in a game called "Impossible Creatures" and I've tampered quite a bit with them.
BASH
I almost missed this one. The language used for Linux scripting and automation! I cannot forget that I used this during my networking courses.