I need a 100+ mW card for my laptop that I can attach an external antenna to (preferably a small parabolic hand held), and point it at my house from a few hundred yards away, maybe even 500-800 to pick up my signal from my house. Noone lives between his house and mine.
Another consideration may have significant advantages.
The solution you propose requires that your laptop always be situated where there is a good (direct line of sight) radio path to your home. Things which interfere with that are great distance (which your "few hundred yards away" qualifies for), walls, obstructions like parked cars, trees, etc.
Which means that what you want to do will probably work if you use it sitting in a second story room with a large window facing your house. The only other places might be out on a second floor balcony or on the roof! Obviously those are serious limitations.
The way around all of that is to use a repeater. The repeater is located anywhere that provides a good radio path to your house, and then your laptop need only be within range of the repeater instead of the house. Hence if the only place it can work is placed in the small upstairs window, you can put the repeater there instead of the laptop!
One caveat with repeaters though... they tend to be picky about the AP's they'll work with. So get one of the same brand as your AP. Or you can replace the existing AP with an AP and repeater known to work. (Two Linksys WRT54G routers, with third party firmware to enable one of them as a router, are an example known to work well. A more expensive combination, that will work out of the box, is a WRT54G AP and a WRE54G router.)
800 yards is apx .5 miles. If your wireless source has line of sight The hawking HWU54D will just do it but you may need to move it around while watching the signal strength till you can optimize it. as someone already indicated - it has a 6db antenna (every 3db doubles your power) the cable is about 6' long and supplies data/power to the transducer in the antenna so you have no rf loss thru an rf cable like you would face adapting an antenna to a PCMCIA wifi adapter card in your laptop
- order a passive usb extension $5.00 from same vendor to save on shipping -the extension is only about 9' for a total of 15' - if you need longer you would need active extension about 15' (similar to usb hub gets power from the usb port but "repeats' the data which eliminates the degradation and you can still now add a passive into it for up to 30' remote mounting.