The Organization of American States (OAS) has several mechanisms for participation by Indigenous Peoples. 
To make these systems more known, it recently released a guide "Participation of Indigenous Peoples in the Inter-American System: Mechanisms and New Tools Proposed." The publication summarizes the participation mechanisms that exist for Indigenous Peoples in different areas of the Organization, including the possibility of registering as civil society bodies, attending the meetings on the Proposed American Declaration on the Rights of Indigenous Peoples, participating in the human rights protection and promotion system, and participating in the Summits of the Americas process. The report can be downloaded here.
