Before the end of each academic year it will be worth you considering how you are going to dispose of your unwanted items as the university / residence provider will not be grateful if you leave things in your accommodation - both for your summer holidays and once you graduate. Anything that is 'past it' and can be binned should obviously be thrown away but how about those other items, which were 'essentials' before and have now become unnecessary?
Maybe you could consider donating these items to a charity shop or a homeless centre? Or maybe earn yourself a bit of extra cash (which you could no doubt always do with!) by selling them on eBay or Gumtree. If the items are not in a good enough condition to sell on, then you could always contemplate donating them on Freebay or Freecycle so whilst you get rid of your unwanted things, someone else will benefit.
Here is a list of example organisations (many of which will have a shop on your local high street) which will happily accept your donated items:
British Heart Foundation
Cancer Research UK