The most popular and worth-while day trips from Munich are:
The Neuschwanstein Castle near Füssen. 90 mins. South of Munich by car or about 2 hours by train.
Garmisch-Patenkirchen, also about 90 mins South of Munich by car or about 2 hours by train. This was the site of the 1936 winter Olymics and home to Germany´s tallest mountain, the Zugspitze, which is almost 3.000 m high (almost 10,000 feet).
Salzburg is also only 90 mins from Munich by car, or about 2 hours by train.
Berchtesgaden is about 2 hours from Munich and just up the road from Salzburg. This is where the famous Eagle´s Nest is.
Teegernsee is a wonderful lake and vacaction area only about an hour from Munich by car, or about 90 mins by train.