I'd be careful. I read an article not too long ago (I don't remember where, though) about ISPs shutting down accounts because people were illegally sharing them through wireless connections (if I remember right, mostly in San Francisco and Chicago, but I may be wrong). Also, I've had some pretty bad experiences with wireless networking because of obstructions. I ended up purchasing amplifiers and antennaes to service the areas I needed connectivity at. Also, if you want to use an external antennae and/or amplifier, you're going to need the right kind of wireless router, because many of them do not support external antennae. I recently set up a friend with a Linksys wireless router with an external yaggie (simply because she was on a tight budget) and it works very well. Just make sure you do your research for equipment and check your service contract with your ISP about sharing, because you may be suddenly without Internet access if they find out about it.

AJ