I built this completely with materials found around my house.
This is NOT meant to cool down a whole room, it just creates a nice cool breeze.
Coleman Personal8 Cooler (or similar)
Small, cheap styrofoam cooler (usually under $10) will also work.
3 PVC elbow joints, about 1/2 in. ID (around $1 each at hardware store)
Drill with bit same size as OD of PVC elbows
Computer fan (about $5 from radioshack)
12v transformer* (not sure where to buy these...)
6 empty gatorade bottles
Duct tape (about $10 from radioshack)
Extension cord w/ switch (not totally necessary, but nice to have)
*transformer only necessary for a 12v fan, you can get a different one for different voltage fans of just install a plug if you have a 120v fan.
Step 1: Cut Hole for Fan
Put the fan up against the back of the cooler, mark with pencil around the outside of it, and cut out a square hole for the fan. Push the fan into the hole. A tight fit is good; it lets less air escape.