You built a madwifi package, and modprobed your modules,
by the look of your post. Now, here's the problem. Slackware's
network configuration does not allow for interfaces other than
eth0, eth1, etc...
I'm running Slackware -current, and have an Atheros 5212 mini
PCI in one lappy. There are two things I can offer.
First, if you want to get the scripts to work, I'll give you a link
to a guy who has this stuff worked out. No need in me repeating
it when you can get the stuff from him.
Second, if you don't want to deal with the scripts now, even
though that's the proper way, you can put this in rc.local
ifconfig eth0 down
iwconfig ath0 essid philemon channel 6
ifconfig ath0 192.168.1.42 netmask 255.255.255.0
route add default gw 192.168.1.1 dev ath0
You should of course change the name of your essid, channel, and
also the IP, netmask, and gateway for your box.
Either way, try it and post back if you need more help.