DFDS also sails to Oslo from Copenhagen. Fjord Line is another company with service between Denmark and Norway. Scandlines connects Denmark with Sweden and Germany. The Eurail Scandinavia Pass, for travel anywhere within Scandinavia (Denmark, Sweden, Norway, and Finland), is valid on some ferry crossings.
DFDS Seaways. Dampfærgevej 30, Copenhagen, 2100. www.dfdsseaways.dk.