Help me figure out my European vacation plans! College student on a budget...up for the challenge?

I'm trying to plan an itinerary for a three week or so European vacation. I am a 22 year old student and would like to spend less than 2500 (not counting airfare to Europe). I know that's possible, especially in Europe. I'd like to visit England, Italy, Germany, Netherlands, Belgium and Greece. Does anyone else have any other good suggestions? And which parts of these countries are not to be missed? Your input is greatly appreciated!