The Enterprise Addressing System (EAS) is a web-based application for storing street addresses in a city. Street addresses are linked to a city's assessor parcel fabric and street network, and validated geospatially. Government employees across different agencies can add, query, update, and retire street addresses in one centralized system. EAS enables more accurate and efficient permitting, tax assessments, enhanced city construction and redevelopment planning as well as saving the city substantial expense through reduction in errors and duplication.
EAS is an open source project -- see http://code.google.com/p/eas.
EAS is currently in production at City and County of San Francisco.