Sqitch is a database change management application.
Sqitch is not integrated with any framework, ORM, or platform. Rather, it is a standalone change management system with no opinions about your database engine, application framework, or your development environment.

MySQLTuner is a script written in Perl that will assist you with your MySQL configuration and make recommendations for increased performance and stability.

dbv.php is a database version control web application featuring schema management, revision scripts, and more!

Alembic is a new database migrations tool, written by the author of SQLAlchemy.

Liquibase is an open source database-independent library for tracking, managing and applying database schema changes

Freesound is a collaborative database of Creative Commons Licensed sounds. Browse, download and share sounds.

MySQL database management tool

Impel takes the pain out of working with HTML5 asynchronous databases.

Statement callbacks? Transaction callbacks? One-to-many and many-to-many relationships? How the heck do I deal with all without my head exploding?

BaseX is a light-weight, high-performance and scalable XML Database engine and XPath/XQuery 3.1 Processor, which includes full support for the W3C Update and Full Text extensions. An interactive and user-friendly GUI frontend gives you great insight into your XML documents.

A Lawnchair is sorta like a couch except smaller and outside. Perfect for HTML5 mobile apps that need a lightweight, adaptive, simple and elegant persistence solution.

Web based MySQL administration

A community-curated database of well-known people, places, and things

PHP Object Relational Mapper

ActiveJS is a JavaScript application framework that provides local and REST based data modeling and pure DOM view construction with back button and history support.

ActiveRecord for JavaScript (ORM)

Extremely lightweight alternative to heavy phpMyAdmin for quick and easy access MySQL databases.