Zillow has released an application for iPhone users that builds on their Zillow API, the Microsoft Virtual Earth API and the iPhone's GPS capabilities. The Zillow iPhone app detects your location and shows data about nearby homes, including market values, photos, and which ones are for sale. It's a great example of a mobile mashup application that uses multiple APIs in meaningful location-aware context.
Developers working with geo mashups should take note: geospatial startup FortiusOne has said that "geocoding should be a commodity" and has announced that it has released a new open source geocoder. If you're not familiar with geocoding, it is the process of assigning geographic coordinates to a location (typically an address or place name).