There are many tools available for MySQL DB. Some of them are really helpful for performing different kind of tasks for MySQL database. Like for database administration, we can use MySQL Enterprise Monitor (which is coming with MySQL Enterprise version and it is paid version too). http://www.mysql.com/products/enterprise/monitor.html
In the Open source technology, one of the best tool is the new version of MySQL Workbench (provided by MySQL). This tool is providing all 3 tools which are useful for admin, developing and ERD creation tasks. In older version, these all 3 things was coming separately by MySQL but now its combined in one.
For the Database administration some more GUI tools are available.
For the Database comparison or Data comparison, following are the best tools which I have ever worked.
For the Backup/Restore purpose,
Actually, Maatkit is a toolkit for MySQL users, developers, and administrators. It provides many scripts for performing specific tasks in MySQL.
Scripts for MySQL Replication like,
mk-slave-delay —-> Make a MySQL slave server lag behind its master.)
mk-slave-find —-> Find and print replication hierarchy tree of MySQL slaves.
mk-slave-move —-> Move a MySQL slave around in the replication hierarchy.
mk-slave-prefetch —-> Pipeline relay logs on a MySQL slave to pre-warm caches.
mk-slave-restart —-> Watch and restart MySQL replication after errors.
Scripts for backup/restore,
mk-parallel-dump —-> Dump MySQL tables in parallel.
mk-parallel-restore —-> Load files into MySQL in parallel.
Scripts for checksum and sync process,
mk-table-checksum —-> Perform an online replication consistency check, or checksum MySQL tables efficiently on one or
mk-table-sync —-> Synchronize MySQL tables efficiently.
mk-checksum-filter —-> Filter checksums from mk-table-checksum.
Kontrollbase is little bit hard to install on the DB servers but Its really very helpful for monitoring and performance tuning of the MySQL DB servers. It has email alerts facility too.
Nagios and Cacti are perfect for monitoring stuff. Specially Cacti is providing graphic functionality on the basis of server statistics so, we can easily identify all over performance of the server through graphs.