I just wanted to say that I have successfully connected my neighbour of500ft away to my wireless network using a USB 802.11b dongle inside a cantenna. My greatest thanks and appreciation go out Jeff Liebermann and Bob Alston for their advice and ideas - I would never have thought that a $25 USB dongle and an old can would have been able to do this for us... That is just too cool. :-)
I will try to post take some pictures the next time I am at the neighbour's house, so you can see the rig we have set up. It's interesting that we are just on the fringe of being able to use just a cantenna with no AP-side antenna's... we often get "low signal" or "no signal" but enough bandwidth for good downloading (the Network control panel settings show 11Mbs connection - not sure if it's lying or not, since we have such poor "signal" readings) and that's all that matters to us. I am still amazed that it worked at all!!!
So, thanks again guys!