SymmetricDS is web-enabled, database independent, data synchronization/replication software. It uses web and database technologies to replicate tables between relational databases in near real time. The software was designed to scale for a large number of databases, work across low-bandwidth connections, and withstand periods of network outage.
log4jdbc is a JDBC driver that can log SQL and/or JDBC calls (and optionally SQL timing information) for other jdbc drivers using the Simple Logging Facade For Java (SLF4J) logging system.
SQL Workbench/J is a free, DBMS-independent, cross-platform SQL query tool. It is written in Java and thus it should run on any operating system that provides a Java Runtime Environment.
It's main focus is on running SQL scripts (either interactively or as a batch), graphical query building or administration of the database is not the focus.
Do you hate starting on a new project and having to try to figure out someone else's idea of a database? Or are you in QA and the developers expect you to understand all the relationships in their schema? If so then this tool's for you.
SchemaSpy is a Java-based tool (requires Java 1.4 or higher) that analyzes the metadata of a schema in a database and generates a visual representation of it in a browser-displayable format. It lets you click through the hierarchy of database tables via child and parent table relationships. The browsing through relationships can occur though HTML links and/or though the graphical representation of the relationships. It's also designed to help resolve the obtuse errors that a database sometimes gives related to failures due to constraints.
Here are some of the best free MySQL tools out there. The description is not my review of the product, it is just what the developers say about their tools. If you know some other good ones, you can drop a comment.