Eclipse SQL Client for database querying/browsing any JDBC compliant database. It supports plugins with specialized functionality for individual databases (Oracle, DB2, MySQL, PostgreSQL, Sybase, Informix) and can be extended.
jDBA is database administration tool being written in Java. It will be able to manage multiple instances from a variety of DBMS such as Oracle, Informix, Sybase, MySQL, and others. Development is currently focused solely on Oracle.