This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Yes, you can open connections to different databases using different drivers at the same time. I don't think an example is necessary; simple duplicate the code you use to connect to your database and change the parameters - done!
Class.forName() registers the forName()'s parameter class with the DriverManager once and only once; and these drivers map specific URLs onto themselves. "jdbc.drivers" system property contains them actually too.