If you want to do heavy duty wireless, a company called trango (
http://trangobroadband ) makes some outstanding WISP (wireless internet service provider) devices. For your circumstances, I'd recommend a 5830 AP and 5530 foxes. Each fox can have its bandwidth adjusted based on your needs.
If you're not looking to spend corporate levels of money, you could do it simply with linksys gear. You can create wireless bridges between linksys wireless G APs, and at each house tie another AP or wireless router into the bridged unit. There are many points of failure in this setup (either side of the bridge goes down, or the true access point/router), and managing bandwidth could get tricky, as I doubt $50 linksys units allow you to limit bandwidth.
As mentioned above, if you're close enough, simply using a serious antenna could do the job.
Peace,
JimBass