Much has been written about participatory budgeting over the last 30 years. From humble beginnings in Brazil, it has swept over the globe and is considered by many institutions and governments to be an ideal method of tangibly engaging citizens in the operation of their communities. It has, however, developed beyond the original Porto Alegre model, and the evolution, exportation into different cultural landscapes, and digitisation of the model have posed new challenges for implementers, innovators and supporters. This report, conducted primarily for the Hewlett Foundation with the involvement of the Omidyar Network, examines some of those challenges. The research was conducted from a meta-level perspective, seeking not to replicate the many excellent case-studies on individual instances of participatory budgeting, and instead identifying where additional support for participatory budgeting could be targeted to benefit the community of practice as a whole.