The Prediction API enables access to Google's machine learning algorithms to analyze your historic data and predict likely future outcomes. Upload your data to Google Storage for Developers, then use the Prediction API to make real-time decisions in your applications. The Prediction API implements supervised learning algorithms as a RESTful web service to let you leverage patterns in your data, providing more relevant information to your users. Run your predictions on Google's infrastructure and scale effortlessly as your data grows in size and complexity.
http://socialgraph.apis.google.com/lookup?q=url&fme=1
birdnest is a Twitter API proxy which filter out the unnecessary information off the Twitter response. This result better utilization of bandwidth for Twitter mobile client, primarily for jibjib.
some info on undocumented del.icio.us api calls
