Spindizzy the MUCK is a shared world running on a text-based multi-user textual environment called Fuzzball. It has about an equal mix of both in- and out of- character interaction.
Spindizzy, the world, is a continent sized, flat chunk of planetoid flying through space. The technology levels of its inhabitants vary by inclination and aesthetics from agrarian villagers to post-scarcity metropolitans. Its inhabitants plot with and scheme against each other, or build grand designs to make each other happy against all opposition. Among them are homo sapiens of various sorts, animals of anthropomorphic or zoomorphic shape, machines, living cartoons, walking balloons, and all manner of other configurations.
You could think of the world as a friendly place where people put their philosophies and ethics into direct, expressive action, bumping up and playing along with other folks doing the same thing.