This API can be used to compute a set of readability metrics for a given text. We currently support the following metrics: Automated Readability Index, Coleman-Liau Index, Flesch–Kincaid Grade Level, Flesch Reading Ease, Gunning-Fog Index, SMOG score, and SMOG Index. The service is deployed at Google App Engine and available at https://ipeirotis-hrd.appspot.com/ The code and documentation are available on Github at https://github.com/ipeirotis/ReadabilityMetrics

This is a term synonym discovery service that exploits that structure of Wikipedia redirects to discover almost-equivalent terms. You can try terms like C++, or Hillary Clinton, or Mihapjungguk to see some of the results.