Improve the lighting in your dorm room to make it feel more homelike. Set up a floor lamp to light the whole room as an alternative to an overhead fluorescent. Buy a nice lamp with a shade as an alternative to a standard desk lamp. Put a side lamp on a table next to your bed. You can even string Christmas lights across the top of your window.
Get a rug or carpet to place in the middle of your floor. A nice carpet will make your room feel less institutional and provide additional seating space when you are entertaining.
Rearrange furniture to make a separate seating or living room area. Add floor cushions or a bean bag chair to provide extra seating for your friends. Having a place to relax and entertain will make your dorm room feel more like home.
Change the curtains in your dorm room if you are allowed to do so. Do away with bland curtains and put up your own. Choose a design that reminds you of home. Get brightly colored bedsheets and linens to add some color and life to the room.
Decorate your walls with more grown-up items. Avoid tacky posters and advertisements. Make your room feel like a living room at home with framed pictures and pictures of family members.
Stock a mini-refrigerator with comfort foods that make you feel at home. Keep a steady supply of drinks on hand for when you are thirsty late at night. Being able to get the foods you like and need in the comfort of your room will take away some of your homesickness.