Geoffrey Rockwell has written a post introducing etcML (Easy Text Classification Machine Learning) a new, freely available, text analysis tool developed at Stanford. The tool’s “primary mode of analysis is ‘classification,’ which you can think of as automatic categorization”:
The tool allows you to pass a text (or a Twitter hashtag) to an existing classifier like the Twitter Sentiment classifier. It then gives you a interactive graph like the one above (which shows tweets about #INKEWhistler14 over time.) You can upload your own datasets to analyze and also create your own classifiers. The system saves classifiers for others to try.