Wireless Lan antennas are mostly better than the buildin antenna of a pcmcia card. More range because of a better position the the antenna. Here you will find some links to interessing site in the net. Most of them will show you some easy self prepared products for less money and a huge range. If you have more interesting links to antennas for 802.11, don`t be afraid and send me a mail. I will link them here. Have some fun ;-)

GERMAN
8 dBi Rundstrahler für WirelessLan
Lucent Range Extender to Outdoor Omni Conversion