Neighborhood scale planning and design in many areas of the United States has been evolving toward a system of negotiated priorities and agreements. Common models include public workshops and design'charrettes'which bring diverse stakeholders (citizens, land owners, developers, consultantsand public officials, for example) together to develop a mutually acceptable plan. Crucial to the quality and effectiveness of the outcome are decision support tools that help this diverse audience understand, communicate, collaborate and make decisions about complex and often emotional issuesof land use and design. Net Energy Communities (NEC), the project summarized in this paper, creates a suite of computer based tools for this purpose. NEC links three types of computer software: the spatial data manipulation, modelling and visualization capabilities of Geographic Information Systems (GIS), the illustration and information retrieval capabilities of multimedia relational databases and, the simulation and comparison capabilities of spreadsheet-based calculation models, into four tools: a site modeller, an elements of neighborhood database, a scenario modeller and ascenario calculator. This paper reports on the NEC project as an example of decision support tools for public participation using illustrations and examples from a 420 acre demonstration neighborhood design in progress for the City of Corvallis, Oregon, USA.