Geocode.Service - The code and data to implement Geocoding web services: translation from a physical location (lat/long, OSGB, UTM) to postcodes, cities and countries and back again. The initial implementation is .NET version providing a SOAP entry point. [BSD License] - http://sourceforge.net/projects/geocode/
TerraService - The Microsoft TerraServer .NET Web Service is designed to simplify the task of accessing TerraServer programmatically. - http://terraservice.net/