The best way to learn about major open source databases (e.g. MySQL, PostgreSQL, etc.) is to attend developer and user conferences. Sun Microsystems sponsors many of these conferences and events. (This April, you can catch Sun folks attending the MySQL conference in Santa Clara, and in May, you can catch them at PGCon in Ottawa.) Finally, if you're interested in Sun technologies and databases, you should become a member of the OpenSolaris Databases Community and start contributing.
Alternatively, you can learn about OpenSolaris at one of the many Sun Tech Days happening in the world!
The Tech Days help you develop skills in Solaris Operating System, Java SE, Java EE, Java ME and Netbeans. With attendants from start-ups to Fortune 500 companies, they offer the best place to share knowledge, evaluate technology, and to engage in participatory learning. Don't forget Web 2.0 at Java University Training.