I’m not a .Net programmer (I’m still stuck in the primordial ooze that is VB6), but if you are, you might want to check out GMap.Net, a free and open source .Net control for embedding online map services in Windows applications. You have the option of displaying maps from Google, Yahoo, OpenStreetMap, Bing or ArcGIS, with tile cacheing an option for faster performance. Several demo apps are available to show what you can do:
One quick tip: right-click and drag to pan the map (took me a while to figure that one out).