The ipl2 is a trusted source of information about a broad range of topics as well as a great source for general homework help. The site is maintained by volunteer librarians and library school students.
From the popular Discovery Channel, Discovery Education allows you to browse for help with Science, Math, Social Studies, English and more. Or take a break from homework and enjoy a few fun games.
The World Factbook from the Central Intelligence Agency is a great source for information on history, government, geography, and transnational issues.