radioshack sells both AC and DC fans. AC is just as simple as getting your standard plug and wire it to plug right into the wall. Nothing fancy. DC requires a little converter box that they sell. Your fan will have a amp rating. Something like 300mA. If your running one fan only you can get a smaller DC converter that will handle 300mA. If you want to possibly run 2,3,4 fans get the bigger converter with a higher mA rating. That way you can save yourself some money down the road and keep your wireing simple using your DC fans in parrellel off of a 1800mA DC converter. You can even canabalize stuff like printer or computer power cables. to get your dc converter. Just make sure your matching Voltage, and it can handle the amperage.
I prefer AC fans. Just a little more flexable options.