Hey Jim,
I did the whole European graduation trip last summer. Three whole months...
Here are some places you can't miss:

-Munich - great city, but about 2 hour train ride south is the Neuswanstein Castle... it was the model for the Walt Disney World castle,the tour through it isn't so great, but the surrounding area is wonderful for hiking, seeing waterfalls, and hanggliding.

-Florence - I stayed in a wonderful hostel right on the outskirts of the town,in an old mansion that was handed over to the state 4 years ago. There are marble frescos and beautiful fountains all over the estate. Wonderful!

-Rome - Make sure you go on the Rome-ing Tours. My friends and I actually took 3 of them. The pub crawl is great!

-Pompeii - Mt.Veseuvius (sp?)is the only active volcano in Europe, you can hike up to the top, then check out the remains of the city. Stay in Naples, which is an often missed town, but be careful, because it is slightly dangerous. We were mugged walking back from dinner one night.

- Greece - Cofu: The Pink Palace if you want to feel like you are still in college at a typical frat party. It's really a rip off for Greece since it's 25 dollars a night, when you can go right down the street and get your own apartment for 6 dollars.
Santorini: WOW, ultra romantic, perfect place to go with a date. Beautiful beaches, and the most amazing white houses with blue roofs.
Ios: 24 hour party...

- Cinque Terre - A string of 5 fishing villages,very small and quaint, the perfect get away if you can get there when the tourists are gone. I stayed in Riomaggiore, the smallest town. You can get a room for about 12 bucks from "Mar-Mar" Do the hike between the towns, even though it is a little tough at some points, it's worth it for the views! The water is incredible.

- between Nice and Monaco - this whole strip is incredible. A train runs every hour between these two cities and stops at several small towns in between. Make sure you check these places out. Many celebs have huge houses along the route, and you can find some great hostels that not too many people know about!

- Pamplona - if you are in Spain from July 6-14, the running of the bulls takes place here. Definately an experience not to be missed!

OK, I have so many more places and stories and recommendations, but I don't want to waste space here. Send me an email if you are interested. Have a fantastic time on your trip. Make sure you keep a journal so you can remember everything!!!