GeoPlanet Explorer. You can explore the geographical information provided by Yahoo in the GeoPlanet API and data set.
uDig is an open source (EPL and BSD) desktop application framework, built with Eclipse Rich Client (RCP) technology. The goal of uDig is to provide a complete Java solution for desktop GIS data access, editing, and viewing.
Geopaparazzi is a tool developed to do very fast qualitative engineering/geologic surveys. Even if the main aim is in the field of surveying, it contains tools that can be of great use also to OpenStreetMappers as well as tourists that want to keep a geo-diary. Geopaparazzi is now available on the Android Market. Search for geopaparazzi on your phone or get it from the online android market.