Always read the "About Us" or "Who We Are" section of an organization's website, but don't stop there.
To get further information from different perspectives, look for names of people and organizations in the content of relevant books and articles, then search those names in both scholarly and newspaper databases.
Additional sources for information:
Digital Public Library of America (DP.LA)
Brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world.
Human Rights Documentation Initiative (HRDI)
The UT Libraries' Human Rights Documentation Initiative (HRDI) is committed to the long-term preservation of fragile and vulnerable records of human rights struggles worldwide, the promotion and secure usage of human rights archival materials, and the advancement of human rights research and advocacy around the world.
Human Rights Library
The University of Minnesota Human Rights Library houses one of the largest collections of more than sixty thousand core human rights documents, including several hundred human rights treaties and other primary international human rights instruments. The site also provides access to more than four thousands links and a unique search device for multiple human rights sites.
Human Rights Web Archive - Columbia University Center for Human Rights Documentation & Research
This archive from the Columbia University Center for Human Rights Documentation & Research is an effort to preserve and ensure access to freely available human rights resources created mainly by non-governmental organizations, national human rights institutions, and individuals.
National Security Archive
Founded in 1985 by journalists and scholars to check rising government secrecy, the National Security Archive combines a unique range of functions: investigative journalism center, research institute on international affairs, library and archive of declassified U.S. documents ("the world's largest nongovernmental collection" according to the Los Angeles Times), leading non-profit user of the U.S. Freedom of Information Act, public interest law firm defending and expanding public access to government information, global advocate of open government, and indexer and publisher of former secrets.
NATLEX - International Labour Organization
Database of national labour, social security and related human rights legislation. Records provide full texts or abstracts of legislation and citation information. Records are indexed by subject classifications.
The Torture Archive
An ongoing project of the National Security Archive, is assembling at a single location documents from wide-ranging sources on United States government policy toward rendition, detainees, interrogation, and torture.