A book club / reading group where people pledge sats to read and comment on the papers listed at the Satoshi Nakamoto Institute (https://nakamotoinstitute.org/literature).

After some time, if people achieve their pledge, then the sats gets returned to original sender. Otherwise, if it's a no show, then the sats go to a charity/pool.

A similar idea can be done for fitness training or a new kind of university.