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.
Mashup contests can be a good way to reveal the variety of applications that are possible when the developer community is provided with a quality API. At the recent BarCamp London 5, Stefan Magdalinski, CTO of MOO.com, ran a weekend-long MOO API hack competition. The MOO service and API let users submit custom designs that can be printed onto products like business cards, sticker books, postcards, etc. These products can then be sold through an online store.
Cycling in the UK is not only a popular past time but and also a real commuting choice. The UK has numerous defined cycle routes and many towns and cities have designated cycling lanes and more recently London introduced a cycling scheme fondly referred to as Boris' Bikes after the current Mayor of London. Since more and more people are using a bicycle as a preferred method of transport, and with cyclists having a different selection of routes, on top of the ordinary street network, than alternative transportation methods, it makes sense for there to be a need for a bicycle journey planning web application and API.