XNavigator is a Virtual Earth browser and viewer for http://osm-3d.org
XNavigator is the online viewer for the OpenStreetMap Globe at http://osm-3d.org and much more. It is an interactive 3D viewer and integrated client for exploring virtual city and landscape models. A wide range of interaction and navigation possibilities makes it easy to visualize and analyze very detailed virtual urban environments. XNavigator is the first application that supports the Web3DService (W3DS) service interface.
QuakeMap GPS mapping program - see quakemap.com and download free trial there. This is a complete Open Source version (no different in features than the commercial version). You can compile it in Visual Studio 2008, enhance it to fit your needs.