After my middle aged Macbook G4's Wi-Fi died on me I first bought a Belkin USB wireless adapter, which was fairly cheap, but I soon regretted the purchase. First of all the adapter is far too accident prone, sticking far out of the Macbook's side, so the slightest pressure put far to much stress on the flimsy USB connector.
Even worse was the incredibly horrid software, apparantly ported by the chip manufacturer. The user-interface not only looked ugly, but was seriously broken as well. Worst of all it had a serious case of amnesia, being unable to recall basic preferences such as favourite networks or WEP passwords. Having to enter the password every time I connected (or awoke the Macbook from sleep) was bad enough, but having to do so repeatedly -- as the adapter kept dropping the connection despite strong signal readings -- soon became an insufferable nightmare.
After a little searching I found the Sonnet 22Aria Extreme. A bit on the pricey side (for 802.11g) it did on the other hand promise seamless integration with my Macbook G4. I also liked the fact it uses the PC card slot (which is unused in 99% of the world's Macbooks) as this anchored the card well withing the laptop casing, This ensures that any accidents to the card do not do addtional damage to the computer.
Best of all, the Sonnet Aria worked as advertised. I just popped it in and a few moments later I was onlinem having only to choose the network in the Airport menu and enter the password (saving it to my Keychain). That was it. It has worked without a hitch for a month now and I can thoroughly reccommend it, especially for those of us doing our bit for the environment with legacy computers! Having a solid, well engineered product which just works without the least effort on my part made it well worth the price.