Unfortunately, there are very few natural language processing techniques that really perform well in practice. But even these few, are not well understood by most programmers. I think that’s quite a shame, because none of these techniques is really hard to grasp. The following demo is a good starting point for demystifying natural language processing.
There are currently 4 Python NLTK demos available. On the top left you can do sentiment analysis, which uses text classification to determine sentiment polarity. On the top right, you can see how different word tokenizers work.