Google Fusion Tables is an experimental app that offers a Java library to interact with the REST API. The aim is to avoid the creation of HTTP requests and the parsing of responses. Highlights include calls to the API, OAuth 2.0 authentication, and Google App Engine support. Created to run on Android 1.5+.
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.
As business computing migrates to SaaS applications, developers must address the problem of the data silos the software creates. APIs let you move data in and out of these online applications but, they present a new set of problems: managing data in several applications using several APIs.