You can count on a dorm room containing two single beds, two desks (usually with a book hutch above), two desk chairs, two dressers, two closets, and a trash can. You can also count on a mirror and a place to hang wet towels. Beyond that, things vary widely.
Wait 'til you get his housing assignment, then check with the college to find out these things:
Does his room come with bunks/lofts or just plain beds? This varies widely. If he's going to have just plain beds, are lofts allowed? These're sold online, or you can make a homemade version inexpensively. If homemade, lofts must usually be inspected by dorm administrators.
Will his bed be extra-long? Most college beds are, so they require extra-long sheets. Don't neglect a mattress pad, an extra blanket, and plenty of pillows for reading in bed. Don't go overboard with linens. 3-4 bath towels, wash cloths if he uses them at home, and one set of bedsheets. He won't have storage space for more.
Will his room be carpeted? If not, a small area rug (at least by the bed) is worthwhile. If the room is carpeted, the dorm will probably have a vaccum cleaner that can be checked out from the security guard in the evenings; this is much better than storing even the smallest model in a small dorm room.
Is his dorm air conditioned? If not, or if his personal temperature runs 'specially hot, he might want a fan.
What appliances are allowed? Refrigerators are pretty much always allowed and microwaves are usually okay. Things that create a hot surface, though, are often forbidden (toasters, electric fry pans, etc) because some kids are so new to cooking that they'd do foolish things like put an electric toaster on their bed. Dorms can't afford the fire hazard (and as a parent, I'm sure you agree!). Also, most dorms have a small kitchen somewhere in the public areas.
Before you decide what appliances he needs, consider the meal plan he's going to have and the within-walking distance food available to him. If he's going to have an all-you-can-eat 7-day meal plan, he won't need the ability to cook much in his room. If he's likely to make a bag of microwave popcorn once a week, he can go to the trouble of walking to that public kitchen rather than having a microwave of his own. On the other hand, if he's not going to have a weekend meal plan and will probably eat microwave dinners on Saturdays and Sundays, a microwave of his own will be appreciated.
One food-related item that's certain to be used is a reusable water bottle. Most college campuses are very "green", and they discourage water bottles that end up in landfills.
Will he have wi-fi service, or will he need cords to connect to the wall? What other computer equipment is recommended? Probably a printer. Don't neglect a small selection of office supplies: A stapler, printer paper, a calendar. Of course he'll want a backpack for carrying to class. He probably has one now, but be sure it'll hold his laptop for late-night trips to the library. Is he taking a math or science class? If so, he should bring the graphing calculator that he already has for high school math. If he's not taking such a class, I'd consider leaving it home.
How many outlets does his dorm have? Likely the building is old and he'd appreciate a power strip. Make sure it's a good one with a built-in surge protector.
Choose a battery-powered alarm clock that won't need an outlet (which may or may not be placed in the right spot for his bed, especially if it's lofted).
What lighting is already built into his room? He can count on an overhead light and maybe a built-in light above his desk, but he will certainly need at least a bedside light. Depending upon the type of bed he has (and whether he has a bedside table), a clamp-lamp might be best.
Will he have a bath connecting 2-4 rooms, or is the bathroom down the hall? If he has more of a "private bath", they usually have to clean it themselves, so he will need cleaning items. If it's a "down the hall" type bathroom, there'll be maid service to do this.
Will he have a sink in his room? This is more common in the older buildings. If he does have just a sink, one pack of Clorox wipes will do for the year.
What kind of storage is provided in his dorm? Plastic milk crates are the best storage for dorms. They make moving in easy, and then they can be stacked as bookshelves, placed by the bedside as a night table, or placed in the closet as organizers. 6-8 of these isn't over-kill. Remember that he will need to be able to store a fairly large number of textbooks.
A small number of Command hooks would be useful for hanging this and that in just the right spot.
Where's the laundry room, and what laundry items will he need? Buy dark towels that can be washed along with jeans (because one person doesn't usually have a whole load of jeans).
Will his dorm have a secure spot to lock up his valuables? I'd be very willing to buy my child a small lock box for her wallet, ipod, camera, etc. It's very easy to walk down the hall "just for a minute" and stay an hour . . . and then come back to find something missing. Or, worse, to have the roommate do this while she's in class. Most importantly on this topic: Get a laptop lock cord. These secure the laptop to a desk, a chair, a bed (can be used in the dorm or carried to the library). Sure, the thief might be able to walk away with the chair AND the laptop, but he's going to be obvious. When I took my daughter to a college Open House a few weeks ago, I was talking to a police officer about crime on campus, and he said that BY FAR the most common crime on campus is laptop theft.
Then have him contact his roommate to coordinate the big items: Refrigerator, microwave, TV.
Before I'd spend big money on dorm stuff, I'd ask him this question: How long does he see himself living in the dorms? Obviously, that's a bit of an unfair question because it may not be what he expects, but if he's feeling pretty sure that he's going to Rush and live in a frat house as soon as possible, I'd be skimpy on investing in things like a loft and a nice 'fridge. On the other hand, if he says, "Probably two years at least" or if you have younger children who'd probably use those items, I'd be more willing to spend more money, knowing that those big-ticket items would be used again.
Don't bring too much of anything. Dorm space is small, and he won't appreciate stepping over things constantly. Make his life easier and live by the mantra "Less is more". Remember that he must move this stuff in /out multiple times, and he must store it over the summer. It's better to bring too little and add stuff later.
I'd help him make a list, but I'd let it become HIS PROJECT. Not all lessons are learned in a classroom, and a kid who's ready to go away to college is ready to set up a dorm room.