Tools specific to individual databases are also listed under those databases - see the databases page.
Navicat
Navicat is available for MySQL, SQL Server, SQLite, Oracle, and PostgreSQL.
SQLMaestro
SQLMaestro is available for ODBC, MySQL, SQL Server, Oracle, PostgreSQL, SQLite, Firebird, Sybase, DB2 and MaxDB.
EMS SQL Management Studio
EMS SQL Management Studio is available for MySQL, SQL Server, PostgreSQL, Interbase/Firebird and Oracle. EMS also provides data export/import and database migration tooling.