GMap.NET is great and Powerful, Free, cross platform, open source .NET control. Enable use routing, geocoding and maps from Google, Yahoo!, Bing, OpenStreetMap, ArcGIS, Pergo, SigPac, Yandex, Mapy.cz in Windows Forms & Presentation, supports caching and runs on windows mobile!

SharpMap is an easy-to-use map rendering and display engine, including AJAX-powered ASP.Net UserControl and a WinForm 4.0 control.

GPS Track Viewer makes it easier to import and display track data from GPS devices. It is designed to be versatile, elegant and fast and supports various formats, e.g. TCX and GPX. You can browse through your data easily, viewing time, distance, average speed for selected ranges