So I decided to use WPA2 Personal with AES+TKIP on my new Linksys WRT54GL router after my old D-Link router died. However, there were some issues in getting it to work on Kubuntu 6.10 Edgy Eft with my Intel Wireless IPW3945abg.
So I decided to put my /etc/network/interfaces and the /etc/wpa_supplicant.conf files up here for reference:
Suppose BLAH is my ESSID name. The psk value is an altered value for elucidation purposes only:

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
eapol_version=1
ap_scan=2
fast_reauth=1

# WPA-PSK
network={
ssid="BLAH"
proto=WPA RSN
key_mgmt=WPA-PSK
pairwise=TKIP
group=TKIP
psk=aaaa3fa7bbbbccccf6d44e199ecb2bebccccad25a0778beeee104db0b3fffff7
}

The value of the PSK command was obtained by using the value associated with the prefix “psk=…” after issuing the following command:

# wpa_passphrase BLAH passphrase
network={
       ssid="BLAH"
       #psk="passphrase"
       psk=aaaa3fa7bbbbccccf6d44e199ecb2bebccccad25a0778beeee104db0b3fffff7
}

The /etc/network/interfaces looked like this:

auto lo
iface lo inet loopback

auto eth1
iface eth1 inet dhcp
wpa-conf managed
wpa-driver wext
wpa-ssid BLAH
wpa-ap-scan 2
wpa-proto RSN
wpa-pairwise TKIP
wpa-group TKIP
wpa-key-mgmt WPA-PSK
wpa-psk aaaa3fa7bbbbccccf6d44e199ecb2bebccccad25a0778beeee104db0b3fffff7
pre-up wpa_supplicant -Bw -Dwext -i eth1 -c/etc/wpa_supplicant.conf
post-down killall -q wpa_supplicant

Once I was done with this configuration all I had to do was, issue the following command to get wireless working with WPA2 and TKIP:

# /etc/init.d/networking restart