Io, the most volcanic body in the solar system. It has a close elliptical orbit around Jupiter, and the changing strength of gravity as it orbits stretches and squeezes the planet, with the resulting friction being able to keep the core molten.

Io has a molten interior but nothing like plate tectonics, magma pretty much just erupts straight upwards through the crust across the surface.

Several other moons like Europa, Enceladus, and maybe Titan are expect to have something like tectonic plates and maybe subduction in their icy crusts, but in detail it wouldn't be quite the same as what we see on Earth, in large part because it's occuring in ice and water rather than rock.