I went ~7 years ago on one of those "see Europe in 21 days" highshool trips. The whole trip was amazing. We actually flew into Frankfurd via Chicago (loooong boring flight).
Here is a Map I googled for just to get a good reference.
http://www.lonelyplanet.com/mapshel...any/germany.htm
Places to go:
Heidelberg - really cool town. Has a fort/castle that you can tour. Has a nice shop district with pubs, etc. You can hang out next to the river at a nice, peaceful park.
Munich - Beer! Beer! Beer! This city has a big Octoberfest. Its beer halls are great (be sure to check out the Wheat beers (Vice Beir as they call it). We went to a Löwenbräu beer hall next to the train station that was a blast. If your into being humbled at all, check out Dachau, a Nazi Concentration Camp which is close by.
Neuschwanstein castle - One of the most famous castles in the world. Its well worth a trip just to check it out. Cinderella's castle in Disney was modeled after this place.