Hitler was a hit in the beer halls of Munich where he got his political start. The Munich City Museum (Münchner Stadtmuseum) has an exhibit that traces the history of Nazism and there are tour companies in Munich that offer tours of Hitler's Munich, traces the origin and development of Nazism. There are some good tours in Munich that take you to Hitler's old haunts and provide a lot of information. You might want to take one of the tours with Radius Tours or with Munich Walk Tours. You may want to also take a trip to the Dachau Concentration Camp a little ways outside of Munich. many of the tour companies combine Dachau with their tours of Munich.
In Nurenburg (Nürnberg), you can visit Hitler's old Nazi Rally Grounds in what is now Luitpoldhain park. Congress Hall in Nurenburg is home to a Nazi Documentation Center, you can combine a tour of the location for the Nuremburg trials at the same time.
The town of Berchtesgaden, near the Austrian border, was an enclave for many of the Nazi leaders and is where Hitler built the famous Eagle's Nest, the Camp David of the Nazi party. The site is open to visitors (mid-May-Oct), but there is little there. On the other hand, the nearby Obersalzberg Nazi Documentation Center, including a visit to the bunkers that were built into the mountainside.
Berlin has several monuments and memorials including the Jewish Museum Berlin. The Topography of Terror exhibit illustrates SS tactics (in the ruins of the former SS/Gestapo headquarters, near Checkpoint Charlie. There have been some excavations in Berlin, one being a huge underground room preserved under glass in the center of the town square on Unter den Linden. For some interesting juxatpositioning, go to Wansee and tour the house where the "Final Solution" was plotted then visit the Reichstag and the German Resistance Memorial (Gedenkstätte Deutscher Widerstand). If you really want to learn about the Nazis in Berlin, take a tour, there are several companies that offer different tours, New Berlin Tours offers private tours of the top Third Reich sites or you can tour by bike with Fat Tire Bike Tours - a fun way to see Berlin and the tour guides are great.
