Google recently announced the Display & Video 360 API. The API supports the company’s consolidated marketing platform and was designed to provide access to asynchronous Structured Data File (SDF) download functionality. Google has announced the first significant round of updates to this API.
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.