For the latest on long range USB antennas, check out the updated version of this article.
Enhancing the wireless range of your laptop using a long range antenna will let you search and find more (potentially open) wireless networks as you travel the world. The typical wireless card in a Macbook gives you about 100mW range. Forget about the technical details but consider that a long range wireless card gives you 3-5 times (300-500mW) the range. This lets you bum Wi-Fi signals from networks that might have been out of your range otherwise.
There are two good options for long range wireless antennas with some minor differences between the two. This isn’t a sponsored review, I just like and find these two antennas personally very useful.
These cards aren’t the easiest to find, but I’ve purchased both from Rokland.com (here’s the link for the 300mW and the 500mW). You can also use the card for Wi-Fi hacking, but you don’t need any extra equipment to search for hidden wireless networks in airports or bus stations.