Note, you can not use Ndis wrapper drivers. Because Nios II can not run x86 binary.
You can use [[media:/OperatingSystems/UClinux/AlteraPCI|AlteraPCI] (or mini-PCI adaptor) for 802.11b/g devices. In the kernel config you have to enable Drivers->Network->Wireless Lan for your driver. You can look at the Kconfig file to find out more devices supported, eg, Broadcom 43xx, Realtek etc .
You should try out this driver on your Linux PC first. Try out the wireless tools utility, and make sure everything works fine. Then make clean to try on Nios II. I made a ptaches for uClinux-dist-20060803. Change the kernel and module location otherwise.
┌────────────────────── Wireless LAN (non-hamradio) ──────────────────────┐
/> route add default gw 192.168.1.220 # my wireless AP
/> ping 192.168.1.254 # another node on my LAN
192.168.1.254 is alive!
Note, if you have ethernet on board, eg, smc91c111 or dm9000 enabled as eth0, then the wireless device may be next free eth device eg, eth1 . If your wireless AP is protected, you may have to give SSID and "key" .
iwlist eth0 scanning # find available APs
iwconfig eth0 ap auto essid "Your SSID" key "your key" # connect to an AP, see man page of iwconfig