I enjoyed sending D little valentines, like the ones they had in elementary school, and candy for her to distribute in her dorm. I did it her first year, now it doesn’t feel as appropriate as her friends are scattered around different dorms this year.
She lost her favorite Camelbak water bottle recently so I sent her a new one. If I’d not had it shipped directly to her, I’d have put some valentine candy in it 
Kind of in opposition to the sentiment of the occasion, but I sent my DD a feminist t-shirt. She’ll love it.
Remember that the US Postal Service has excellent priority shipping for various sized boxes (we used an envelope to send a t-shirt once). I agree that sons are difficult to shop for. When son was in college I sent him frozen grocery store cakes via UPS because the distance meant next day delivery. The USPS works better when it is a long distance- 2 days Tampa to Seattle!
Just dropped off a priority flat rate box from shipping from AZ to VA. DD should get it Monday (I’m always surprised how fast she gets her mail on campus). The box contained: homemade cookies, Mike and Ikes and Sour Patch Kids (ordered by my DD), a photo of me and our dog (HA! a little taste of home), a picture of her brother and his friends (she had requested a printed copy of one I posted on FB), and a card with $20 inside. DD said my sister (her aunt) sent a valentine’s box as well. (That was nice!)
I’ve done 2 group care packages with the moms of D’s four best friends. We just did a valentines one. We each brought a card for all the moms to sign. Each mom brought a couple of small items for each girl- candy, room decorations, body lotion, etc. It’s a great way for the moms to stay connected. We had wine and appetizers and put the boxes together. The girls loved that the moms were all thinking of them.
I have been known to hide Girl Scout cookies in the back of the freezer so as to unexpectedly produce a box of Samoas in the off-season. 
But it’s actually the season now, so maybe not as exciting at the moment.
Lots of great ideas here! My kiddo is a sugar hound, so any candy goes over big – doesn’t have to be expensive, even, as a $6 tub of Red Vines is as exciting as a 4-pack of truffles. She also loves silly socks/undies, new markers or pens, fun buttons to put on her backpack or bulletin board, decorative tapes (duct or washi), stickers, toiletries/makeup, books… One time I got her a jar of KindNotes (Google them) and that was fun. Oh, astronaut ice cream! I think it tastes like styrofoam, but the kids like it (and it’s a lot more portable than real ice cream).
Really anything they would’ve liked at home is great now, too.
Love all your great ideas! Remember to buy some heart stickers and put them all over the outside of the box or envelope. Although it may embarrass our students in the mail room, secretly I think they like it. It’s a nice embarrassment. I only do a care package 3 times a year–a month after school starts, Valentine’s Day, and Birthday. Gift cards to favorite restaurants like Denny’s and Dominos are good. A pink and red care package would be fun. Use lots of heart or pink and red tissue inside. I too always add a kids’ holiday card with some cash. Always appreciated, I think…by the size of their credit charges, I think they prefer cc for everything tho!
Some ideas for boys (or girls):
Cards Against Humanity. Deoderant, Toothpaste, and new socks. Steam card. A blow up sled if in snowy area.
I know someone who stuck 4 nips in her kid’s care package (enough to share with roommate). I’m not advocating that but I bet he liked it.
I always send something for her roommate too
Maybe something from your hometown that they can’t get in their college town? Our local ice cream shop will send ice cream in a cooler with dry ice. Of course, that is pricey and would probably have to be for a special occasion. But I’ve sent cans of the local restaurants’ chili, barbecue sauce, etc. to out of town relatives before (no kiddos in college yet) and that’s been a hit.
Patriots Super Bowl LI t shirts–share the love.
When I send DD something, I send her boyfriend Pez candies. I sent them to her once and he ate them all. Turns out he loves them. He also likes socks, sports shirts and blankets (no accounting for taste, he likes the Giants).
I send my DD Amazon Prime boxes with toilet paper, oatmeal, granola bars, baking stuff, and other weird stuff I find as I scroll through the pages. They usually have a deal where if you buy 5 items off a special list, you get free shipping.
^^I sent my daughter some blue diamond almonds. A boy in her dorm ate the whole can. He said he had never had them before and couldn’t believe there could be anything so good. Now, I always include a can for him too.
I have sent my D a few orders of Edible Arrangements when she was in the dorm. It is pricey but she shares. One time she was really sick. Since there was a local store near the university, I called the local store directly and ordered her a small arrangement which made the afternoon delivery. She said she ate most of it herself.
I always send “theme” boxes to my daughter…Halloween, Valentine;s day, I “O-FISH-ally miss you” (all fish themed items). I’m getting ready to send a finals snack pack (She’s on quarters). I always decorate the flaps of the box with my Cricut. Look on Pinterest for some CUTE ideas! I put in snacks and always some silly things like sidewalk chalk, a small toy etc. Can’t always be serious! She loves them and her friends envy them! My son will be at college next year. He won’t are and I might just sent the ones from Amazon that are all snack food! If you are doing your own box, go to the post office and get a free box that costs the same amount no matter how heavy it is. One price as long s it fits in the box!
For a beginning of the year care package, I sent my daughter’s friends a package with a large mug, packets of chamomile tea, a cute bear mini container of honey, cough drops, packets of Advil, and Theraflu-they will get sick at some point! I put all those together with cellophane and then included other typical care package items like Kraft mac-n-cheese that only needs water to be put in the container, hot chocolate, nuts, candy, popcorn, etc… I also included gloves bc they were So Cal kids headed to the east coast. For birthdays, I send My Cup of Cake (cake in a pouch), a See’s sucker in this cute packaging they have now that says Happy Birthday and a gift card of some kind.