I've had 7 dorm rooms over the course of 7 years of boarding school and college, I have pictures of my best setups somewhere but I'm having trouble finding them. I'll post if I find them.
There's been some good advice in the thread. In all of my infinite wisdom (

)I will suggest:
- Warm floor/desk lamps. Forget about the fluorescent ceiling lamp it sucks. I replaced mine with 48" blacklight tubes soph year of college, great for pregaming.
- Big leather highback deskchair. A pain in the ass to get it to school, yet beautifully ass-pain free for the rest of the year.
- Cheap blankets/sheets. Your bed is a couch as much as a bed, and will be abused.
- Maximum quantity of posters. I've picked up a few at the fall term poster sale every year since '02, and can completely cover the walls of a large room in posters. Takes the edge off of cinderblock walls and makes your room feel like your room.
- Rug. If your room is tile floored, you'll want it.
- Folding camp chairs. I got a few at Dick's for $5/each a while back. You can stash them under your bed and instantly have seating (with cupholders!) for a lot of people if you want.
Pili said:
One word of advice, don't make your room a hang out room. You will regret it the entire year after the first month or two.
That's totally personal preference. I love having people in my room all the time, even if they're just laying on my bed reading a magazine while I'm on the computer. All of my friends know that if my door is unlocked they don't have to knock. I don't do any homework in my room, only in the library, so I can separate the two and still get things done.
This year I'll finally be out of the dorm and into a college owned apartment in a nice old victorian house facing campus.