Need to be a little more specific. But as a rule of thumb, get a card listed...
Need to be a little more specific. But as a rule of thumb, get a card listed as supported at this site:https://help.ubuntu.com/community/WifiDocs/WirelessCardsSupported and pick one that allows for the user of external antenas. Then make sure your wireless access point also supports the use of external antenas, and then you can purchase some high-gain directional antenas that might help you get a few extra yards of distance in a particular direction.
Otherwise, to *really* extend your range you'll have to break out the soldering iron and violate FCC regulartions.
Also, you may want to consider something other than 802.11a/b/g/n if you are really concerned w/ distance. Gernally, the lower the frequency, the better the range for the same transmission power. So, there are technologies that use the 800 - 900 Mhz band, though I'm not sure how string you're allowed to transmit there. There's also 802.11y which uses the 3.1 Ghz band, but allow for *string* transmission and allows you to get MILES of range (but the gear is pricey).