i'm currently running a cheap belkin wireless 802.11b router, which can be upgraded to something with a greater range.
no trees or building in the way.
thats all the info i could think of off the top of my head. This doesn't have to be a cheap setup either, as were looking to keep the connection for the next year or two if it works.
I'd get a second AP with a directional antenna towards his house. This would be the easiest, no screwing around method. I've been sharing my Internet connection with my friend who lives in the apartment building across mine, about 200ft. away. It works great even going through a couple of walls with an omni antenna mounted outside my window, and he has a cantenna I made a couple years ago.