Defcon, the hacker conference in Las Vegas held each year, established what might be a world record in Wi-Fi links: 55.1 miles: I wouldn't want to be standing between (or near) the two points, but it's a great achievement in the best hacker tradition. The winners of the second annual Defcon contest were teenagers--even better! I didn't realize the Guinness Book folks were monitoring these kinds of records; they say the world distance record is 192 miles, but it required a Swedish weather balloon. (Or a weather balloon in Sweden, to sound less kinky.)
Let's not forget the Snipe Yagi, a Yagi antenna mounted inside what looks like a rifle with sniper sights.