Superset is a free and open source data visualization tool, developed by Airbnb team for internal business needs, which you can harness its powers for your visualization analytic needs.
It's a very interesting project and we are testing it in our playground section (we will publish a demo in the next days).
Superset can connect to multiple data sources via SqlAlchemy, with some special features for Druid datasources and clusters connections.
More information on Superset on the project's page on GitHub.com.
The product is also available on Heroku, or you can run a Docker image demo for testing.