Fundbucket is a nonprofit service that allows donors to easily donate to other nonprofits through organized "buckets" of organizations grouped by sector or custom categories. Donors allocate percentages of their donations to each nonprofit in a selected bucket. Fundbucket uses metrics like social return on investment to calculate recommended donation weights for each nonprofit to guide donors. This approach aims to make fundraising easier for both donors and nonprofits by streamlining the donation process while promoting donations to effective organizations.