In testing out the Dockerfile for building the docs, I noticed it created an asf-site/docs/latest directory at the end. Out of curiosity, I went to http://arrow.apache.org/docs/latest/, and it reports a version of 0.11.1.dev473+g6ed02454, which is not close to "latest".
I'd like to see this "latest" site get updated automatically. I'm working on getting this Docker setup complete (cf. https://issues.apache.org/jira/browse/ARROW-5497), and once that's working, it should be feasible to add a Travis-CI job to update /docs/latest on every commit to master to apache/arrow.