A simple script using pyFirmata to talk to an Arduino Uno with a joystick plugged into it. See http://thinkpigeon.blogspot.com/2012/12/joystick-and-arduino-uno.html for details and images.

Tkjoy.py

from Tkinter import *
from pyfirmata import Arduino, util

SERIAL_PORT = '/dev/ttyACM0'
DIM = 300

def read_pins(xpin, ypin):
    x = xpin.read()
    if x is None:
        x = 0.0
    y = ypin.read()
    if y is None:
        y = 0.0
    return x, y

def _coords(x, y, r=2):
    x, y = [int(DIM * n) for n in (x, 1 - y)]
    return x - r, y - r, x + r, y + r

def update(k):
    x, y = read_pins(analog_0, analog_1)
    #print '%0.2f . %0.2f' % (x, y)
    k.coords(dot, *_coords(x, y))
    k.coords(line, org, org, int(DIM * (1 - x)), int(DIM * y))
    k.after(33, update, k)

board = Arduino(SERIAL_PORT)
it = util.Iterator(board)
it.setDaemon(True)
it.start()

analog_0 = board.get_pin('a:0:i')
analog_1 = board.get_pin('a:1:i')

style = {
    'fill': 'green',
    'outline': 'white',
    }

t = Tk()
c = Canvas(t, bg='black')
c.pack()

c['width'] = c['height'] = DIM
org = DIM / 2

dot = c.create_oval(*_coords(.5, .5), **style)
line = c.create_line(org, org, org + 1, org + 2, fill='white')

update(c)
t.mainloop()