Greek Islands (by Liz)

Santorini is a must. If he's only got time for one stop - this is it. Keep in mind it's a 16 hourish ferry ride, so get to Piraeus (the main port outside of Athens) early.

Ios, either one or two ferry stops before Santorini, is one of the big party islands.

Mykonos is also a big party island, although it is popular with the wealthier gay groups. Whether that's a good thing or a bad thing is up in the air.

If you get the chance to go over to the Adriatic, go to Corfu, home of the beloved Pink Palace in Agios Gordios (just make sure to take the ferry to Corfu city.) If going from Italy to Greece, or vice versa, this would be a great mid way.

Definitely spend some time in Athens, and by some time, I mean a good part of a day. The Acropolis is expensive, (when I was there pre-Olympics, it was 15 Euros, which with the current exchange rate is hideous) and there's not really much to see, but the view is spectacular. Keep in mind to bargain with the cab drivers, and I recommend cabs since keeping track of where you are on a bus when everything is written in Greek is a pain in the ass.

One big tip - don't bother with booking a place in advance when you're in the islands. There will be people at the port advertising their small, family-owned "hotels." We got our people down to 8 euros. This is assuming you're not going in August, when the majority of central and southern Europe go on vacation and head to the beaches and islands.