DBeaver is free and open source (GPL) universal database tool for developers and database administrators.

Usability is the main goal of this project, program UI is carefully designed and implemented.
It is freeware.
It is multiplatform.
It is based on opensource framework and allows writing of various extensions (plugins).
It supports any database having a JDBC driver.
It may handle any external datasource which may or may not have a JDBC driver.
There is a set of plugins for certain databases (MySQL and Oracle in version 1.x) and different database management utilities (e.g. ERD).