Well as with most bits, the most expensive is usually the best but id just slap a standard Netgear card (54 or 108) in unless you’re after uber gain jobbies and attachable aerials.
If you get the Belkin PCI card (F5D7001) it can support speeds of up to 125mbps with the g-nitro. it is only compatible with other Belkin G-Nitro devices. I got one in my for sale thread. Otherwise if you want the standard 108mbps, you'll want the Netgear one as its most reliable and will give a good wireless range.
The best would have to be Orinoco cards they are expesive though but great gain and the laptop cards allow for an external antenna hooked up to it for even more gain.
