This free handbook (199 pages) on participative action research, focused on agriculture (Participatory Rural Appraisal) is useful if you want to explore all tools and techniques. It is very practically oriented and contains lots of examples.
UK-based research organisation Intrac summarises the main advantages and tools related to participatory action research. Useful if you want to learn more, but are limited in time.
This extensive online guide helps you to monitor progress, conduct surveys, gather community-level indicators, and other methods for evaluating comprehensive community initiatives.