MapWindow is a free, extensible, programmable open source geographic information system. Originally developed at Utah State University, it's now developed and maintained at Idaho State University.

MapWindow is a fantastic alternative to expensive solutions like ArcGIS or  MapObjects. The desktop application is a complete solution allowing you to work with GIS data in a comfortable, intuitive manner. MapWinGIS is the underlying powerhouse, which renders the map and provides comprehensive data access APIs. While some data formats are natively implemented, many of the data formats are made accessible through the use of GDAL (Geospatial Data Access Library), another fantastic open source API.

The MapWinGIS component is an excellent tool to add GIS capabilities to an existing application, or jumpstart development on a new application. If the desktop MapWindow application almost does what you need, it is highly extensible with a plug-in interface. A custom plug-in can provide additional functionality and let you make it suit your needs.

Because the tools are released under the Mozilla Public License (MPL), you can use these components in your commercial applications too. The only requirement is to mention it in your license agreement somewhere; and it's customary, but not required, to mention it in your product's 'about' box.

If you'd like custom MapWindow plug-ins, customizations, or MapWinGIS development done, contact me and I'll be happy to discuss it!