For maximum effectiveness, you would need some sort of dish or directional antenna on both ends. I really have no idea what I'm going to do with that dish. Since I don't have a place to put it (I live in an apartment!), there's no good way to use it for anything. What I am more interested in though, is getting 2 direct tv dishes or something like that, and using them. If I stick a little heatsink and fan on my router for cooling, I should be able to double the transmitter power without any serious problems, or so I understand. I think the default for most wireless routers is between 24 and 28 milliwatts. Not a whole heck of a lot of power. That, along with a dish at both ends should be plenty to get a signal the 9 or so miles to my friends house.
On the other hand, I have seen a 1 watt amplifier for 2.4ghz signals. It was only like $300 I think. That, along with some good antennas would send a signal a LONG way. Of course, then I would have a deal with the FCC... That might not be fun.