A Cooler, Cold Water and Copper Tubing Here's a video that shows you how to set up this dorm-legal A/C hack. Or check out this post with plenty of how-topictures.
A Fan Blowing Into a Cooler Try this one, from Instructables user hleon Fill the cooler with ice (or ice packs) and set up the fan to blow directly into it (without falling in, of course. You're trying to cool down the bedroom, not electrocute yourself). Cut out a few vent holes in your direction and you're good to go. (It should be noted that you don't need a cooler for this to work. It's the best at keeping melted ice and condensation off your wood floors, but you don't need the insulation for this to cool you down, as evidenced by our last "hack"...)
A Bowl of Ice and a Fan All you need to cool a small space down is a source for cold air and something to blow it around. Simplify both of these ideas and just drop a bowl of ice in front of your fan, just like our own Campbell showed you in this post.
They all work somewhat the same way—by putting ice or ice water right in front of a blowing fan—but you can figure out which version works best for you. One thing to note about all of them, though: They only do a good job of cooling your room if that room is far away from the source of the ice. A freezer actually warms the air as it's freezing water, so your homemade A/C won't do you any good in the same room. But if you need to cool a small, localized area—like your bedroom as you fall asleep—each of these projects is a great way to get it done without spending big bucks. (Top image: Flickr member CarbonNYC licensed for use under Creative Commons)