the least expensive option (either purchased or fabricated by you) is an immersion chiller. it will chill your wort somewhat quickly (depending on batch size) and give you a decent cold break. you don't know how much you're gonna love this thing until you use it... like a bottle washer. it also doesn't require gravity or a pump for operation, as the water flow from your sink/hose does the work. a step up from this is a counterflow chiller, which is pricier and runs the wort through an inner tube, surrounded by an exterior tube that cold water is run through in the opposite direction, making it more efficient and faster. even better, and more expensive, is a plate chiller, which is a little box with H2O-chilled steel plates but operates like a counterflow chiller. this is the fastest, most efficient and most comparable to commercial systems.
one more option (no, i'm not going to say ice bath) is a hybrid chiller, and this is a DIY contraption. It is effectively a counterflow chiller, but instead of the exposed tube-within-a-tube idea, you are basically running your wort through a tube coiled to a diameter just less than the inside diameter of, lets say PVC, piping, which again, cool water is running through the opposite direction. never made one myself, but mr. papzian outlines the basic design components in his book, and claims effectiveness. only benefits to the hybrid i can see are that its less expensive than buying a $200 counterflow device, and you have variable exposure to w20 depending on the length of PVC you use and the number of wort coils within.
good luck and cheers!