You may find these links helpful.

• Stuart Hurlbert: President, Scientists and Environmentalists for Population Stabilization:
  Who Said Academics are Hopelessly Timid or Hopelessly Globalist? Slides | Text
• Carrying Capacity Network
• EcoFuture Population and Sustainability
• Liquid Fuel, Population, and Liquid Energy Supply Per Person
• Terrain
• U.S. Sustainable Population Policy Project (USS3P)
• WildEarth Guardians