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.
The popular picture-sharing empire behind I Can Has Cheezburger lets you view, caption and share funny images. You can do this via its sites and, the now, thanks to their API, you can do it via code (technical details at our Cheezburger API profile).