American Society of International Law's (ASIL) Electronic Information System for International Law is a comprehensive database for primary documents, websites, and research guides - a great first-stop for finding international agreements; search by title, subject, keyword // has a human rights section
Organization of American States
Official site - contains official documents, treaties, legal opinions, resolutions, declarations, news, etc. English, Spanish, Portugese, French.
United Nations Treaties Collection
Includes databases for United Nations Treaty Series (UNTS), Multilateral treaties deposited with the UN, Status of Treaties (MTDSG), Certified True Copies (CTCs) of treaties, Depositary Notifications (CNs), and more