If you don already have the appropriate drivers, OpenLink Software is the place to go for ODBC drivers for both Windows and Mac platforms. They have 30-day trial downloads so you can try before you buy.
JDBC is Suns Java-based cross-platform database access technology. Suns main JDBC page gives a nice overview of the technology. Youll also find a link to Suns driver database. It lists available drivers for dozens of different databases.