Organizations are categorized into three embedded tiers. Those in higher tiers (lower numbers) employ many of the same tools and objectives that characterize groups in lower tiers.
Even if your area is not served by an existing organization, check out these websites as they contain very useful information.
Groups creating truly sustainable, high quality-of-life communities (Tier 1)
These organizations work with their communities (city or county) to identify optimum population levels and proactively lobby government officials for land use policies to achieve and maintain those levels:
Groups that proactively work to control growth (Tier 2)
These organizations do not yet have an end-game in mind with respect to optimum local population levels. But they do proactively lobby government authorities for land use policies that minimize growth and new development in their communities:
Organizations that advocate for "smart" growth management (Tier 3)
"Smart growth" organizations focus on where growth should happen. They champion development policies such as building "up" rather than out, minimizing sprawl, cluster or conservation development, putting high density development near transportation arteries, etc. Many are allies of the Growth Machine and are funded by development interests. Although growth management is better than no growth management, these organizations still accommodate growth and so will not enable the creation of sustainable, high quality-of-life communities. However, you may want to partner with smart growth interests to implement certain land use policies. Your county's Planning Board, or a Planning Board in an adjoining jurisdiction, can often refer you to a smart growth organization in or near your community, if one exists.