Postgresql Community
PostgreSQL
FreeComprehensive Database Management with PostgreSQL
Mac
SQL Server Express
FreeSQL Server Express: Powerful Free Database for Development
WindowsSQLite Database
FreeSQLite: The Tiny Database Powerhouse
WindowsMariaDB database server
FreeComprehensive Overview of MariaDB Database Server
WindowsSQLite Database
FreeComprehensive Overview of SQLite Database for Mac
MacPostgreSQL Database Server
FreePostgreSQL: Powerful Open Source Relational Database
Windows
Navicat for SQL Azure (SQL Azure GUI)
Trial versionNavicat: Powerful SQL Azure Database Management Tool
WindowsNavicat for SQL Azure (Database Manager)
Trial versionComprehensive Database Management with Navicat for SQL Azure
Mac