The National Cellular Directory is a people search website that lets users search for a person by name or by phone number using reverse phone lookup. National Cellular Directory Happy Hour People search allows users to search phone numbers (including cell phone numbers) to find the owner behind the number. This free service has an API for developers. The National Cellular Directory People Search API uses SOAP messaging with HTTP POST or GET methods for accepting requests and returns results via XML. Full documentation is available with registration.