Given the horrors of the Nazi regime it is very difficult to even contemplating the idea that anything good was done. By and large Hitler's determination at strengthening German Nationalism and World Domination and horrific events that came with it rightly outweigh any positives of the regime.
During the war, Germany had several technological advances in flight and radar, etc which we still use today. Also, while obtained in the most horrific way possible, the Germans were able to map out the human body and its organ systems at a level of detail never done before. The Nazis used Jews to do this with and while in no way do I approve of the way this information was obtained, it did help move medical science forward and gave us a better understanding of human anatomy.
Also the discover of several pharmaceuticals came about due to testing that was conducted in the concentration camps.
The Germans established that cigarette smoking was cancerous and banned it as a result. They did not have Madison Ave executives trying to trick people into thinking smoking was good like in the US.
There is nothing positive about people coming together to commit mass murder and to destabilize the world. Yet it is still important to remember that most of the people in Germany were really just people like us trying to survive in impossible circumstances who happened to be led by a psychopath and one of the world's biggest mass murderer.