- MySQL Workbench - Query editor, EED editor (graphical schema diagrams), forward/reverse engineering schemas, administration features
- phpMyAdmin - Installed on pretty much every hosting provider and easy to install on your own web server. Neat interface, works from a browser, can connect to any MySQL server on any OS
- SQLyog - available in free and paid versions, lots of features.
- Here is a link to the people that made the MySQL Query Browser and MySQL Administrator tools. DbDesigner4
- You should also take a look at NaviCat - Available for Linux, OS X, and Windows. Although it's not free, it can do many things including converting data to/from other programs and file formats. Also offers support for 5.0 Features (SProcs, Views, etc)
- TOra is an excellent tool but its MySQL support can be a little spotty and newer Qt releases have introduced some compatibility issues. Still, when it works, it's phenomenal.
- CocoaMySQL has been abandoned