Generally the size of a dorm bed is extra-long twin. If the dorm does not provide bedding material, you will need to get extra long twin-sized sheets. The other option is to use the standard twin-sized sheets and use mattress straps to keep the sheets in place.
Check if the school has any requirements for computer power or if there is a preference on the type of computer (desktop or laptop) to be used in the dorm. Add a printer, extension cords, cables, and power strips to your list.
The basic bed, desk and a chair are normally provided by the dorm. Additional items like a desk lamp, alarm clock, and extra seating you'll need to bring yourself. Most dorms prohibit certain electrical appliances. Generally microwaves are okay and toasters are not. A mini-refrigerator, about 2 to 6 cubic feet, could be handy to store a few sodas and sandwiches.
You will need to provide your own electronic entertainment like TVs or game consoles. Confirm the room is big enough to fit any large devices.
Washer and dryers are not always provided by the dorm, and if they are, they may not be located on the same floor. A laundry basket, detergent and other supplies will be necessary. A few rolls of quarters for the first couple weeks of the semester would also be helpful.
Dorm life usually involves sharing a bathroom with other students. Normally there is no place to store personal items, and this is where toiletry bags or caddies are necessary. Toiletry bags are portable and offer storage for essential personal items.