The gifts that didn't get used were the books (sad but true), graduation plagues or mugs, things that didn't match my daughter's color scheme (you'd have to include the receipt if they want a different color), a photo album that was too gaudy, the wrong style of hamper, and picture frames that were too cheesy.
The best gifts were the practical ones. A tool kit came in handy, first aid kit, school supplies (pens, paper clips, stapler, thumb tacks), a hanging jewelry organizer was a huge hit as my daughter has a lot of jewelry (TJ Maxx has some cute ones right now), surge protector, and over the door shoe bag.
Be sure to include the gift receipt if it is something that might not be their style. What sounds like a great caddy idea to you might not be how they want to carry their stuff. E.g. my daughter found some cute tall cloth lined baskets for her laundry while my son preferred the standard plastic basket. I used a drawstring bag in college. My daughter was really into color-coordinating things with her freshman roommate. My son was happy with the most minimal of stuff.
You can always include a Target gift card inside another gift if the value is not as high as you wanted to spend. Those were the most appreciated as Target has so many things they need.