UNA USA contains loads of helpful information on preparing for Model UN conferences, including tips on writing position papers, creating country studies, and even how to dress.
CIA World Factbook
The CIA World Factbook contains extensive information on just about every country in the world, covering topics from the nation's government and economy to their demographics and geography. It is essential that a delegate print out the information sheet pertaining to their country for their country studies.
BBC Country Profiles
The BBC Country Profiles are similar to the CIA World Factbook, though a little less extensive; however, it may contain different information.