Arctype - Free SQL Client for developers and teams. Available for Mac, Windows, Linux, and Web.
PopSQL - Modern SQL editor for teams
Veezoo - Ask Natural Language questions against your SQL Database
SQL Police Department - Learn SQL while solving crimes! Climb the ranks of SQL PD.
Numeracy - A SQL pad that gives you x-ray vision for your data
DrawSQL - Easy database diagrams. Create, visualize and collaborate on your database entity relationship diagrams.