Sentdex is primarily written in the Python programming language, from the website to the sentiment analysis algorithm.
The geographic sentiment analysis globe makes use of Python's NLTK (Natural Language Toolkit) module, primarily for the superbly useful Named Entity Recognition, though NLTK is not used in the stock or political sentiment analysis.
This website uses the Python framework, Flask.
HTML/CSS design is Bootstrap.
The graphs are generated with Highcharts.
The interactive geo globe code is from Google's Chrome Experiments.
For more information on how Sentdex itself works, see: How Sentdex Works.