Side trip from Copenhagen to Malmo or Lund?

A good idea, especially now that you can take a train over to Sweden. Both cities are nice to visit, but Lund is a little easier to get around and has the great cathedral, the University, and some good museums.
There's frequent direct rail service from Copenhagen to Lund (about 45" and the train will probably have a sign for Kalmar). The big highlight of Malmo is now the "Turning Torso" which you can see from the train window as you enter Sweden.
Suggestion: Continue north from Lund to Helsingborg (about 30") and then take the passenger ferry across to Helsingor, DK (not the ferry service from the train station, but the 'passenger only' ferry near the town hall across the way). You'll arrive at a dock between Kronborg Castle (Hamlet's) and the train station. It's only a 45" ride back to Copenhagen.

Thanks Tim - that sounds like a good idea.

Malmö is more modern, Lund has more of an older university feel about it.

Malmo is awesome, the little square has great restaurants and best people watching, cruise along river is pretty good to. Enjoy