A few people have mentioned retroactive public goods funding. I'd suggest broadening the scope a bit:

Better funding models for altruistic projects

Effective Altruism, Research That Will Help Us Improve

Market-oriented funding models are often a poor fit for altruistic projects due to the free-rider problem. On the other hand, traditional philanthropy is limited by available funding and uncertainty about how to best allocate it. Various mechanisms have been proposed to address these problems, including certificates of impact, mutual matching, quadratic funding, and others. We'd like to support work in this vein to (a) design new funding models, (b) evaluate them in small experiments, and/or (c) implement them at scale.