The Twitter API is one of the most popular APIs in our directory. While the most fundamental use of the API is to post a Tweet, developers have been using the API to access and mine the humongous amounts of Twitter data being generated, resulting in 50 Twitter visualizations in our mashups directory alone. These applications mine Tweets to provide services that help users track topics of interest, geolocalized Tweets and even predict flu outbreaks.
Infographics have played an increasingly visible role in communicating complex analytic data in an easy-to-digest way. Until recently infographics were hand-crafted by graphic designers with a special interest and ability in data communications. Visual.ly has made a name for itself by authoring web-based data visualization applications that can be customized and populated on an individual level.
If you want to see in realtime what's going on Digg you can use their digg spy page. This popular Digg feature uses a dynamic Ajax UI to let you see diggs as they happen. And now it serves as a model for a growing number of mashups that use web APIs to give you a realtime window into activity on a variety of services.