Use the Intergovernmental Organization Search Engine (a Google custom search) to search across hundreds of IGO websites:

Use the Non-governmental Organization Search Engine to search across NGO websites. Sites were chosen based on their consultative status with the United Nations Economic and Social Council (ECOSOC) and also collated from University of Minnesota Human Rights Library, Duke University Libraries' NGO Research Guide, and the World Association of Non-Governmental Organizations (WANGO).