GlobaLex, an electronic legal publication dedicated to international and foreign law research published by the Hauser Global Law School Program at NYU School of Law, recently updated a number of its excellent research guides.
In particular, you might find their collection of United Nations resources useful:
“The United Nations is such a massive organization that its wide array of processes and products require enough reference sources to warrant a map and compass for navigation. As a map, here are suggested search techniques for several standard types of queries and, as a compass, here are the U.N.’s many diverse search tools organized into resource types.”
You can find the collection here: http://www.nyulawglobal.org/Globalex/United_Nations_Research1.htm
Credit: Thanks to Library Boy for bringing this to my attention.