Keep in mind, this will not cool off your entire house, or maybe even a room. Evap coolers work best in hot dry climates, when the humidity is very low. The principle however, can cool off an entire house. That being said, become creative, the more air you move through your cooler, the more evaporative capacity your cooler has. I chose this design because it's cheap, simple, and it doesn't require anything other than what I had lying around.
Step 1: Tools and Items.
* Power supply - for this I used a 9.6v power supply I robbed from an old guitar pedal or something. I have others lying around but this one had already been used to power a similar fan, so I felt that it was adequate. A switch would have been a nice touch, but I couldn't find one that wasn't in use.
* Solder Iron - Only needed if you plan to solder and shrink wrap or tape your connections (suggested method). If your not soldering be sure you have an strong connection with your butt connectors and what not. I will not be held responsible for you electrocuting yourself, your children or your pets. Nor will I if you burn your house down. I might feel some sympathy, but I doubt it.
* Swamp cooler padding - Obtainable from any hardware store, this was left over from replacing mine in my big swamp cooler, if you can't come across or afford any, I'd maybe suggest an old cotton t-shirt, sponges could work, but I don't think they'd let much air through them, I suppose you could consider paper towels.
* Fan, shroud, and mounting hardware - The fan was a 120mm computer fan, they're rated at 12v (I know, I know. My power supply is only 9.6v) try to use a fan that matches up with your power supply as well as possible. Computer fans are all 12v. Household fans are almost all 120v (wouldn't suggest this for the inexperienced).
* Shrink wrap, electrical tape (or butt connectors) - You have to isolate those connections from the outside world, or worse, each other. I would suggest the shrink wrap, but your choices are your own. If you choose electrical tape, at least solder the connections and inspect before every use. If you use butt connectors, tape it any way, these things have a way of wiggling themselves loose. I've stopped using them almost entirely.
* Scissors - choose some you don't care much about. Your sister's, mother's or wife's best pair will do perfectly ;) for this I chose some that'd already been sprung, and probably should be thrown away, but they're awesome for cutting random things, and cutting open " Otter Pops"
* Container - This can be almost anything, be sure that it has a big enough surface to mount the fan, the one shown is a disposable tupperware type container (these are very brittle). If using a larger fan, I'd totally suggest a five gallon bucket.
* Screwdriver, pliers and wire strippers - The wire strippers aren't shown here, and I didn't even end up using the pliers, but if I really need to explain these tools to you then maybe you shouldn't try this.
* Drill and bits - At the very minimum you should have a rather large one and one in the range of 11/64 (if using a similar fan). If you're lacking a drill and bits you could possibly get by with a precise cutting instrument and an awl of sorts.
* Heat gun - you'll only need this if you're using shrink wrap, a blow dryer works, or even a cigarette lighter. The gun shown is the type built to remove paint, but it works wonders on shrink wrap in only a few seconds. It's also incredible for scrapping parts from circuit boards, if you're a tinkerer this is a very handy thing to have in your arsenal, and they're rather inexpensive at wal-mart.
* Pile of dishes and dirty working area (kitchen counter) - entirely optional. If you're married you might be in trouble for tinkering instead of cleaning, in my situation the wife thought the baby swampy was cute, and then laid down for a nap. Exercise your own judgement here.
Step 2: Cut Hole for Fan
Step 3: Mounting Your Fan
Step 4: Intake Holes
Clean up the holes as best as you care to, it's not really going to affect the outcome of it, but it looks better.
Step 5: Padding
I wasn't extremely precise through the entire production of mini swampy, and this isn't really a step that needs to be either, It's better to cut the pads a little bit bigger than what you think and then trim them to fit. You definitely don't want air traveling through the container, without constant contact with the pad, that's wasted efficiency. Cut them a little bit big and trim off the excess, use the scraps to fill in gaps and you should be good to go. Don't try to squeeze the pad in there, that would limit it's ability for airflow, just look for the perfect fit.
Once you get them set up, be sure to test the lid, if it's a low lying lid you might need to trim some excess off your pads, on the finished product I had it so the pad was just barely touching the fan shroud, if it's pressing against it hard you could run into problems with water gushing up into your fans motor, and if it's too low, well you're just wasting air.
Step 6: The Fan
The fan shown wouldn't work with my 9.6v power supply, so I had to revert to a known good fan that would work with it. The white stripe on your power supply wires (hopefully there) will indicate the negative wire on your power supply.
Try your hardest to not take shortcuts here, electrocution, damage, or fire could be the outcome. As shown, I soldered the connections and used shrink wrap. Again, I will not be liable or even sad if you electrocute yourself, children, pets, or burn your house down.
Be sure to slide your shrink wrap down the wires before you connect them, for this I used one on each positive and negative, and a larger piece over the top of them.
Soldering is easy enough, be sure that you get a good hot joint, you don't want those to come loose. Using more solder doesn't help much, but making sure you heat the entire connection so that the solder flows through both wires to form a solid connection is what you want.
After the connections are soldered, slide the shrink wrap up over them, and all you have to do is heat it up. I heated the two smaller connections at the same time, and then heated the larger connection over them.
If you're uncomfotable with using a power supply, feel free to use a 9v battery and connector. That should be adequate to run most fans.