As part of my research, I'd like to hear from fellow treehouse students, what is the best programming language to learn

It depends on what you want to do. Do you waht to work as indie or in some company(in this case study info about the company, what languages and instruments they use and go foreward). Well if you want to work more with logic and data better you can study some of OOP languages like C#, Java, Python etc. If you want to make sites start with HTML and CSS and continue with JS or PHP. In reality the languages does not vary so much, they have common principles but different names. For example, I've started with Java and indie small games, then I got a position in a global company that uses C#, in two weeks I already could write something usable by the company though started to study C# at the moment that I agreed to work for the company. I just needed to get used to new instruments that have a lot of in common as well, but it did not took to long. Now in a month and a half a read and correct code of other developers without many difficulties. So it really do not matter what language you will start with, what really matters is to start.