Release date: 9 May 2015
MariaDB 10.0 is the current stable series of MariaDB. It is an evolution of MariaDB 5.5 with several entirely new features not found anywhere else and with backported and reimplemented features from MySQL 5.6.
Thanks, and enjoy MariaDB!
For those upgrading to 10.0.19 from versions prior to 10.0.18, the MariaDB 10.0.18 Release Notes contains a comprehensive list of changes.