Was fiddling a lot a few days ago with many different Docker containers and mounted volumes. Afterwards I found lots of dangling volumes. I got curious on how to clean this mess up and found a solution that worked for me (use at own risk).
docker volume rm $(docker volume ls -q --filter dangling=true)
You could of course run the inner part to just list the dangling volumes and not remove them:
docker volume ls -q --filter dangling=true
//Daniel