I use Linksys WAP54G units with directional antenna at each end for my internet link that comes from my brothers place just over a half mile way.
Outside in line of site from his AP unit I can get a solid connection to his place directly with my laptop and no local antenna or repeater!
Going from my end doing a general scan of signals withthe directional antenna I can pick up all my neighbors home wifi systems within a mile and half from my place despite they not having any antenna on their base units! Most even a mile plus away show up as being 30 - 60% signal too!
Do a eBay search for Wifi antenna and you will get loads of different units to pick from.