National Address Server

If you give the National Address Server (NAS) a valid postal address it will return a properly formatted version of that same address. Leave out a north, south, east, or west reference and the NAS supplies it. Drop an avenue, road, parkway and again NAS supplies it. All of this and the appropriate ZIP+4. There's more features to this site. You can perform person searches, ZIP searches to find what cities are represented by which ZIP codes. The site even includes some limited international address searching.