NetworkManager would be cool, but I'm not sure at all that you can get it's functionality without having a big desktop with a panel applet to sit it into. Gnome comes with it, but Xfce doesn't as far as I know, and that has bugged me too
But setting up WPA encryption is not a big deal. Just get familiar with wpa_supplicant configuration file; in the easiest case (which means often) you'll get away with less than 10 lines in that file, and a wpa_supplicant command with a couple of arguments along with a dhcp client command (unless you use static ip). You can even use wpa_passphrase to generate a basic network entry to add to the configuration file; the rest you can find out by reading the manual page of that configuration file:
Code:
man wpa_supplicant.conf
See the examples for a start.
Once it's done,
Code:
wpa_supplicant -D wext -i wlan0 -c /etc/wpa_supplicant.conf -B
dhcpcd wlan0
and you're done. Change arguments if needed to suit your environment.
Note: you don't have to touch the configuration file of wpa_supplicant after it's done the first time, and for the wpa_supplicant startup you can create a nice script and maybe even run it in the boot scripts to have it work automagically. It's a lot easier than it looks like