Google Earth for iPhone
Google has released a version of Google Earth for Apple's iPhone. While the handheld version does not have all the functionality of the desktop application, (for example it can't yet read kml files) it is really quite remarkable that you can get this kind of access to data on a handheld device. It takes advantage of the iPhone's GPS chip to find your current location and the search feature allows you to search for places and services near your location. It also has the option of noting Wikipedia entries for nearby locations and also photographs geotagged on the photo sharing service, Panoramio.