United Nations Environment Programme (UNEP),
a selection

Commission on Sustainable Development
Site with links to meetings of the Commission, documents on result, earlier meetings and others.

Convention on Biological Diversity - One of the two Rio Conventions
Official site to the Convention with links to the Conference of the Parties, Clearing-House Mechanism, and others.

Intergovernmental Panel on Forests
Site with information on the Panel, it's history, meeting reports and other information.

United Nations Conference on Environment and Development
Site by UNEP with a  background publication on the process leading towards the Conference.

Trade and Environment
Site with a downloadable monograph series on Trade and Environment and background material.