AeroSQL is a free web-based tool for managing MySql servers written in PHP. The key feature of the product is the management of the database content. The result of SELECTs is displayed in a grid as in traditional desktop applications. The grid is editable: you can update cells and save the changes to the backend database server. For now, the query browser represents the main functionality. Additional features will be added in the next versions: administration tools (backup, restore), database object management (create tables).
Visit their homepage at http://www.burlaca.com/aerosql/