The geospatial Web enables virtually everyone to contribute to the growing col-lection of geographically referenced information on the World-Wide Web. In this chapter, we present a Google Maps-based tool that enables Web users to contribute two types of informa-tion: annotations and their reference locations. We further differentiate annotations into obser-vations and opinions regarding specific places. The potential of this approach for integrating lo-cal knowledge into environmental planning was assessed by conducting an online map-based discussion of organic farming among expert stakeholders in the Kawarthas area in Central On-tario, Canada. The discussion contents shed light on the participants’ perceptions of the organic food market. Moreover, the experiment demonstrated how a map-based discussion forum can be useful for obtaining public input on planning and policy issues.