I am very passionate about this...get a mesh shower caddy NOT a plastic one!
I made this mistake my freshman year and got a plastic shower caddy. Here's what happened with that...every time I would shower water would get stuck in the plastic grooves. I would go back to my dorm room, put the shower caddy on the ground, and five minutes later there would be a huge puddle on the ground.
So moral of that all, get a mesh shower caddy because water drains out of it way better. This one is my favorite mesh shower caddy (used my sophomore year). Once you move out of dorms you'll probably throw it away but it is an essential for when you do live in a residence hall.