I personally like LinkSys products, especially since Cisco bought them.
If you get an Atheros 5212 chipset you can use the native madwifi
drivers, rather than a Windoze driver with ndiswrapper.
Jean Tourrilhes is the acknowledged Linux expert on wireless, and Jeremy
even interviewed him. I'd check
his website for hardware compatibility
before I bought it.
Also, I have a friend who works with IBM who's got some good docs
on wireless and Slackware...even has some Slackpacks, and also the
necessary stuff to build your own Slackpackages. In fact, I just installed
a 2.6.12.2 kernel on my lappy and built a new madwifi package for use
with my Atheros 5212 mini-PCI NIC. Check
here and look at not only
the /slackware directory, but also the /rc_scripts directory. He's got docs
for several cards, using madwifi and ndiswrapper.