UN Charter.

Organization Chart of the UN System. 

A link to Membership of the Principal UN Organs can be found using the United Nations Official Homepage, Section Main Bodies.  

The United Nations Today, formerly Basic facts about the United Nations describes the structure and activities of the United Nations and its organisations, and looks at its work under the headings of: international peace and security; economic and social development; human rights; humanitarian action; international law; and decolonization. It also includes details of UN websites, UN member states, past and present peacekeeping operations and UN special observances, as well as giving contact details for UN An abbreviated electronic version is available through
the UN Official Homepage, Section About the United Nations. 

United Nations Handbook -  published annually since 1961 by the Ministry of Foreign Affairs and Trade, New Zealand. This handbook is a clearly ordered guide to the organisations that make up the United Nations, the basis of their structure, their aims and their membership.

The UN in Brief is an electronic introduction to the UN system linking you to the main sites of the United Nations Official web pages.  

Repertory of Practice of the United Nations Organs is an analysis of the decisions of the principal organs and their application of the Charter. It is published by the Secretary-General at the request of the General Assembly. Published volumes for the period 1946-1988 and advance versions of forthcoming volumes are available online at the official web site of the Security Council, where they can be retrieved by year or chapter.