Portable Wi-Fi Antenna for Centrino Laptops?

Quinthar asks: "For years I've been reading of amazing extensions to wifi-range, but they always seem to include external hardware rather than what's built into regular laptops. As wifi makes it almost everywhere, is there anything I can use to eek out extra coverage in the coffeeshops? I've read of USB antennae -- are these snakeoil? If not USB, how else can I plug a real antenna into a simple Centrino chipset without the hassle of an external card? My dream would be a tiny parabolic dish with a tripod that folds up neatly. Does such a thing exist? Can I hold a Pringles can up to the right spot and expect results? Basically, what are my options, and which do you recommend?"