If you are going to be in Dresden, then the closest camp may be Sachsenhausen, which is near Berlin. It is very similar to Dachau. If you go to both of their websites, you will see what I mean. Both were set up as model camps and used for political prisoners mainly at first. I don't know that much about Dachau, but Sachsenhausen saw many religious prisoners like Jehovah Witnesses, priests, nuns, ministers, and also homosexuals, alcoholics, and communists and many 1000's of them lost their lives. Men were held here and the neighboring camp - Ravensbruck held the woman. I would also go visit that one too since they are so near each other. The East Germans used this camp for many years after the war too, and it still has some original buildings, such as the morgue, the autopsy room, the kitchens, the jail cells, two barracks and various other buildings.
They are all very moving and emotional places to visit, so I hope you make it to one of them. They are all "worth while" to see.